Put the "nobody is forcing you to tip" argument into perspective. Nobody is being physically or legally forced to tip. This is true, and I see nobody claiming that either.
But the tipping culture pushes a narrative of what is socially acceptable or good, and if you don't fall in line with that, you are considered one of the bad guys.
Rather than a reflection of the service received, somehow the tip is a reflection on the customer's character. But it is backfiring, because many people, like myself, have stopped caring. Call me a horrible person, but I don't care.
Whereas social norms have pressured me to care in the past, the pushy tipping culture has now trained me -- liberated me -- to stop caring.
The "nobody is forcing you to tip" argument is a red herring.