For deer camo is irrelevant because most cases you have to wear hunter orange (or pink) because you don’t want to die by being shot by another hunter. Also the deer don’t really notice the orange so it works out. If you strictly hunt deer you should focus on staying warm and wear hunter orange, camo doesn’t matter.

For waterfowl and Turkey especially though camo is necessary. Birds are really good at seeing danger so if you don’t blend in you have almost no chance of getting one.

The reason a deer hunter would likely be wearing camo is they also hunt turkey/waterfowl and gear isn’t free so they use a lot of the same gear for both seasons.

At least this is why I wear camo while hunting, I do both, but I’m fully aware it doesn’t matter for the deer. The gear is just good for long duration outdoor activity in all weather.

There is definitely a fashion aspect to camo. Less so in hunting, and more so in the military world. Relevant fashion podcast:

https://www.articlesofinterest.co/podcast/episode/39c00bac/gear-chapter-5

The rare times I have been hunting we wore blaze orange hats & vests with no camo at all. Not getting shot by accident was priority #1, avoiding hypothermia was priority #2.

As someone who lives in northern BC: only city folk/wannabe hunter cosplayers bother with camo. Sweats and sunglasses work fine.

I know several people that dont even leave their truck to shoot unless they actually need to.

I hunt in whaterever I'm OK with getting dirty but I always have a blaze orange hat because someone shot at me when I was a teenager.

People already covered a few reasons deer hunters wear camo (only wanting one set of hunting clothes, camo does work on deer to an extent, etc). I'll add a couple of other reasons.

Many hunting seasons overlap, so someone might head out early on a Saturday morning to their hunting area to hunt for deer then spend the heat of the day hunting birds. Or maybe they have a license for both bear and deer, and they'll take what they see.

Second, camo works on humans. Non-hunters absolutely love to mess with hunters. I have several stories of waking up hours before dawn, driving to a place I can hunt, sitting in a tree stand in the freezing cold waiting for dawn, and then having a random person spot me from the road, then hike up to me to tell me I'm not allowed to be there cause Mr X doesnt let people hunt on his property (despite the fact that I have a signed permission note from Mr X). Or someone who doesn't think hunting should be allowed spotting me and then just letting their dogs off leash through the woods to flush away any deer, despite the fact that if I had a dog with me while hunting, it would be illegal because of how stressing it is for deer to be chased by dogs. Or the DNR officer doing their job by checking to make sure I have permission, the proper licenses, weaponry, square inches of pure blaze orange, etc, and next thing you know, you've lost 1 of the 2 days you'll be able to hunt that season. You only have a few prime hours per day, and having a person show up during that time will keep deer away for the rest of that window.

It's far easier to just hide from people.

Edit: and another thing I just remembered to add, camo lets other people know you are likely a hunter. If you are just walking the woods with shorts, a t-shirt, and a weapon, you will likely freak some people out.