The I.T. industry is infamous for employers requesting overtime from staff but getting away without paying for it. Here's an extract from a discussion thread I came across on SlashDot:
In the IT industry as I've known it, 'part time work' is anything less than 80 hours/week.
Not sure if you are joking, but if not...then you need a new job. Or you may just need to put your foot down. I have been in IT for years as a web developer for a few diff companies, and have never worked like that. Get your stuff done at work, make it clear you are willing to work a little extra where needed (which should be rare) but if there is bad planning, well, tough. IT shops need to be brought back to reality, namely, that poor planning cannot be overcome by stressing out your workers. And I've done pretty well, and thus far my family hasn't starved. The people who are often overworked are overworked because they let it happen. I have known way too many "heroes" who are all willing to work as long as needed for no good reason at all. Trouble is, today's hero is tomorrow's burnout.
Or become a consultant. You may work the hours, but they are no longer a free gift from you to the company. You bill every hour you work.
Any project that requires "significant overtime" is a project that was planned with unrealistic ideas of how much work would be required.
This assumes the overtime is free because the workers are on salary. If the overtime gets paid (even as normal hours instead of 1.5x), then it's possible the planning took this into account and was just willing to pay the price to get the job done in fewer calendar days.
Otherwise, it's most likely a company with employees who aren't able to get jobs anywhere else, so they can't push back against the unreasonable demands of management.