I worked for a company that built its own vacation calendar and ticket system.
They said it was cheaper to build their own compared to contracting with an off-the-shelf system.
And they were right. It was cheap to build.
To maintain it, though, was a nightmare.
The workplace rules and regulations, all the connections with the payroll system (which they built themselves, too)…
It took an entire development staff to maintain and update.
So full of bugs. I spent so many hours getting them to fix incorrect information.
My current job uses an off-the-shelf system.
And everything works.
Including me.