Ok so, wouldn't you want this situation to come up more often, where a prospective employee can get the contract changed? You said you'd rather not have this happen at all.

Except that it won't happen more often because that power imbalance exists. I have some power when negotiating because I'm experienced, I'm very good at something in extreme demand, and I'm knowledgeable about how a business works. Most people don't have two or more of those things.

You describe a senior and socially competent tech worker's delight. Some of us have empathy for those who are not. "Oh, but more people with no market power can 'negotiate'" is not a net benefit for people even if it was a beneficial situation for me.

"In its majestic equality, the law forbids rich and poor alike to sleep under bridges, beg in the streets and steal loaves of bread."