Because lots of people being banned are simply exercising their right to free speech (US 1st Amendment), if they are committing a crime it is up to a countries law enforcement to deal with it, we have justice systems we don't need Twitter and co replacing that with de-platforming and cancel culture. It's becoming like those dystopian sci-fi movies where corporations have taken over as government and so many people don't seem to see it.
This is where I draw the line. Is Twitter essential for life? If someone loses their access to Twitter has their quality of life degraded? No on both counts. Being able to use Twitter has nothing to do with free speech. If you lost twitter access right now, have you lost your ability to speak freely? No, you just can't use that particular platform - that's all. If anyone wants to set up a new 'free speech haven' they are free to do so as it's a free market.
If you were paying for the servers and electricity for a website and someone who says things you, rightly or wrongly, don't agree with, why should you have to put up with it on your platform you created?
If a guest in your house was saying things you don't agree with and you asked them to leave, no one would bat and eyelid. It's just that on a global scale.
Losing access to a social media platform =/= losing your ability to say whatever you want. You just can't say it on a private platform.
If you're all for private companies having so much power via T&C's and to hell with rights and laws then are you okay with a landlord saying that he doesn't want black people renting his property and to hell with anti-discrimination laws? why can't he he's a private business if you don't like it go find another house to rent.
I don't really see it that way. I see it more as you've rented a house from someone, they've explicitly said "no smokers and no pets" and as soon as you've got in you've smoked a 20 deck and you've picked up several dogs from the local dogs home. The landlord see's what you've done and has asked you to leave.
Whos to blame? The landlord or the one renting and breaking the rules?