I recall something about 'hey computers are fun to tinker with' and it was all downhill from there. I have had many arguments with my brother who doesn't understand the 'on call' part of IT work (over one Christmas he said 'Turn your phone off!' when I stated I couldn't as I was on call he said 'no you just turn it off, problem solved' and a heated argument ensued with him saying 'tell your boss to F off and go away'). Once upon a time IT paid well at least to deal with it.
Yep, unfortunately in IT on-call always exists. I'm no longer at the coal face with on-call, although I make it clear to my team that I'm happy to do it if they don't want it. But the money is reasonable, and I think my area have had something like 4 calls in the last 6 months ... so it's money for nothing.
As team leader / manager, I'm also on-call (escalation purposes), but don't get remunerated for that. Have only had a few calls myself.
About 8 years ago when I was more keen, I was happy to put in overtime. I worked some ridiculous hours some weeks (with paid overtime). There were weeks when I was earning $500-1K in overtime and working until 10 most nights and pretty much all weekend. Those days are well gone though...