• Decreased performance, as DRM is often hooked deep into event loops and adds non-negligible overhead.
• Decreased privacy, as DRM often requires pinging an external server constantly.
• Decreased security, as DRM is a black-box blob intentionally meant to be difficult to peer in to, and has been the target of attacks such as code execution vulnerabilities before.
• If you own a game but don't have an active internet connection, DRM may prevent you from playing the game.
• If you own a game but have multiple computers, DRM may force you to buy multiple licenses when you're only using one copy at a time (c.f., a physical CD with the game on it).
• Eventually, a DRM company is going to go out of business or stop supporting old versions of their software; if you want to play an old game that had that DRM, you won't be able to even if you own the game.
• &c.

DRM exists to "protect' the software developer, i.e. protect profits by making sure every copy has been paid for and to force people to buy multiple copies in certain cases. DRM never has and never will be for your (the consumer's) benefit.

I gifted my dad a steam game for his birthday. He is a big Linux fan so he installed it on his Linux system. Now he can't play it for more than 5 minutes before denuvo freezes not only the game but somehow even manages to freeze the complete system and he has to reboot.

Had to return the gift. It's a shame he really wanted to play it

In the case of Denuvo, it is proven to drastically decrease performance for the sake of "security."

Examples:
Hogwarts Legacy Denuvo vs Crack

Resident Evil 8 Village Denuvo vs Crack

When I was about ten years old, I bought the game Warrior Kings while visiting my grandparents using my birthday money. When I got home, I tried to install it on our computer, only to discover that the game wouldn't install because of some DRM thing. Years later, I discovered what really happened was that the copy I bought was apparently not an original disc, but as a kid I had no way to know. I spent hours trying to install it, attempting many times over the next month. The pictures on the box looked so dang cool, but I never did get to play it.

DRM hurts consumers. When you aren't able to use software you yourself paid for, that's a negative. There is no benefit for the consumer, the benefit is only for the seller.

Some DRM systems abuse security designs. Regular applications aren't meant to be running at kernel level (ring 0) and should be running sandboxed at a user level. There are kernel dev blog posts that talk about this. It's basically like making an arm move by poking a brain with a stick. Anything that can then access that stick or the hole you created can make at brain do whatever they want.