Just because others do it doesn’t mean that we all should.
What do they mean by on call? That you should be available on the phone and able to answer questions or that you should be available on a lap top to spend 8 hours re-coding?
My wife does on call for IT projects and it is the former so we’re normally free to be where ever as long as she can be contacted. If it is likely she’ll be needed to actually do something then she will be at work.
Even in jobs with regular hours there are times when this type of thing is called for. I know I have a clause that says I’m supposed to be flexible as occasionally I need to work odd hours. However, my employer is very reasonable in return.