Some people hate bluetooth because almost all phone manufacturers have decided to stop including 3.5mm audio ports on new phones, which forces Bluetooth on people. I think this is reasonable because consumer choice is good.

Some people hate it based on not wanting to have to charge their headphones, or wanting something that works when there's a lot of wireless interference in an area they live/work in. Again, fair enough.

Some people hate it based on outdated or poorly understood bullshit repeated by "audiophiles" about how Bluetooth is bad quality. Most people listen to music via compressed as fuck mp3s or streaming services anyway. It's garbage in, garbage out - most modern Bluetooth compression isn't going to do shit. Even if you are listening to your glorious collection of locally stored flac files, most people will find more difference with the tuning of each individual type of earphone than with Bluetooth as a class. Audiophile opinions should be taken with a huge grain of salt because a lot of these people believe in bullshit like $10,000 HDMI cables which objectively present the same signal as a $5 amazon basics cable.