It can be if you hoard information. However I've seen that often a company doesn't want to (or doesn't have time) to upgrade something and no one wants to work on it. So someone gets "stuck with it".

What layoffs come, it's hard to get rid of that person in the short term.

That does and can change, so don't bank on being the only person knowing that system for the next round of layoffs. Be sure you are working on your career in the meantime.