Do you convert dead organic matter into fertile soil or pollinate flowers? They do. If insect populations were to vanish, so would humans. They perform too many vital functions that humans cannot.

Climate change.

OP literally never leaves the city.

Pollution leads to a decline in the bug population. Pollution = human byproducts (including byproducts of imprisoned animals) causing global warming and climate change affecting habitat; pollution = pesticides and chemicals which make it harder for insects to reproduce; pollution = plastics, trash, and environmental contamination; pollution = human changes that are functionally useful for humans (like roads and farms with pesticides and cities) but may be not helpful for insects.

The joke is that at first, having fewer bugs is nicer because a lot of bugs are annoying.

The joke is also that while it's convenient at first, in another few decades it means EVERYTHING will die, so it's not actually a good thing.

The joke is also the obliviousness of the human driver, who is relieved to be dealing with fewer bugs, not realizing that they are missing for the same reason he's about to become extinct.

There are decreases in pretty much all types of animals that are neither human nor domesticated by humans, and for bugs there are decreases of bees, and there's been discussion that the world is experiencing and extinction event.

Wynn Bruce set himself on fire and died trying to alert people that these trends pose a problem for humankind and no one cared. David Buckel also set himself on fire trying to warn people. It doesn't matter at this point.

The problem is religion. People are stupid and believe in imaginary bullshit that doesn't exist and society accepts this as normal thinking. Psychiatry says bizarre religious thinking is a symptom of schizophrenia, but normal religious thinking is acceptable if enough people believe it (in an unscientific capitulation to popular opinion in a "scientific" field that is hardly ruled by scientific rules). Religion is always illogical and it's dooming us all.

People believe god would never create a planet that could be destroyed and don't understand math or how to analyze scientific data. On top of that, greed caused by capitalism means that for most poor people, they are just struggling to get by and really can't contemplate next year much less 100 years from now.

Most pollution is caused by not only poor resource management and not correctly taking into account externalities of pollution into the markplace in creating government rules (and conservative economic theory means making rules to deal with externalities) but also caused by just too many people. It's sad, but likely some horrible virus like bird flu killing most of the population is the only way in which the planet remains habitable. The fact that only Communist China has successfully been able to reduce their population through non-economic policy declarations (as opposed to restricting resources) is a sad commentary on some of the problems of democracy when so many people just can't understand math and instead embrace religion. (China also is a large contributor to pollution and this is not meant as exculpation of the Chinese Communist Party, but rather a brutal look at how religion has played a large role in decimating the environment.)

If people weren't religious, they could understand these problems. But instead religious idiots take pleasure in making fun of Greta Thunberg as woke because they are literally too stupid to analyze graphs and intelligently assess data. That's okay, if humankind lacks the intelligence to deal with this problem, then war famine and plagues will perhaps succeed since human reasoning has failed. Religion allows these people the comforts and safety of their delusions as a cocoon away from the anxiety and fear caused by dealing with reality, which can be harsh. Unfortunately, people in this delusional cocoon make really stupid decisions so we're probably all going to die.

Often when bacterial populations with limited space and infinite glucose supplies are left to their own, they pollute and pollute and population grows exponentially until suddenly the pollution is too much and nearly all of them die. Glucose = oil; petri dish = earth; colony collapse in a petri dish = 7.99 billion people suddenly dying.

If some horrible disease like bird flu suddenly killed 4 billion people, perhaps AI could swoop down from the metaphorical cloud and help humanity manage resources in time to stop us from all dying, but probably it's too late for even that.

(When you hear Elon Musk say people need to populate the planet even more, I think he knows what is about to happen and is taking the rational position that fleeing earth is the best option for survival and it will be hard to flee earth is everyone is so scared of death they stop working. So his message of "everything is fine, let's increase the population and also thereby pollution even more" is dishonest, but highly rational. I don't know if this is actually what he thinks. His hostility towards trans people also seems strange so I suppose it's possible he is that illogical, but his response to that may be a result of a lack of empathy caused by severe autism, whereas telling people to keep increasing their numbers may be a rational lie so he can increase the likelihood of fleeing earth prior to planetary collapse.)

A certain subset of people have given up on trying to convince people of anything or do anything, figuring it's like arguing with the sun rising and setting and that planetary biosphere collapse is just an inevitable part of nature. Others set themselves on fire to warn people, some people hold cardboard signs and gather and chant and think that will change capitalist societies and wake people up from the delusions of religions, deprogramming people through signs held up by large numbers of people. A lot of people are aware on some level, but don't like to feel existential dread and so they just sort of ignore it.