The expectation that senior developers should be able to work independently is killing the team's ability to collaborate

The more they ask for help the less they feel they are meeting that expectation.

Being able to work independently doesn’t mean getting value sooner. It means people will keep their mouths shut when they are stuck until they eventually figure it out on their own.

Younger folks give their best to try to model the same behavior as they spend more years in the industry, reinforcing the same pattern for people joining the team and industry.

Minimize the perceived cost of asking for help if you want to have a healthy, collaborative environment.