People always underestimate the moat that is institutional agility/ossification. There may be no theoretical moat in software, but every time you switch HR or financial systems you find out the hard way just how many integrations have been built (directly or indirectly) around a specific way of thinking about organizational data imposed by the software containing it, all of which require significant rewrites for the new system's conceptualization. The costs of switching add up fast and the risks of delayed payments/paychecks significant, which is how you end up with companies paying $$$ for extended support on discontinued HR and financial software.
It's the same reason companies will pay for GSuite and O365 subscriptions concurrently because a handful of departments refuse to give up their desktop applications and others have Excel-based workflows that do not work in Google Sheets and do not care enough to learn Python or find someone in the company who can write a better system.