Maintaining it is.
The legacy codebases from this stuff are dumpster fires, because most of the tools are closed enough ecosystems that the companies supporting them have to reinvent every programming best practice from the last 30 years.
'Version control? Sure, that's a feature on our roadmap that we'll get to at some point...'
In addition to going back to the bad old days of limited-use, proprietary compiler problems. 'Oh, that bug? Yeah, just don't do that.'
Furthermore, unless you choose very carefully, you're playing right into vendor lock-in, and a lot of the people buying this stuff aren't technically proficient enough to realize that.
Once these companies hit the end of the easy growth ramp, and the industry turns into monetizing & squeezing existing customers, there's going to be migration pain on an Oracle scale.