A lot of companies have learned the hard way that going against that, when not completely and totally unavoidably necessary..was a bad idea.
My company still uses custom dispatch and freight handling software written exclusively for them back in the early 80's. It's been tweaked and adjusted as necessary over the years to fulfil new functions and such, but it's still basically the glowing green CRT text based system it was back when it was originally built, just running on newer PC's now instead of the dumb terminals and central server setup that was originally there.
It works. Don't F with it. Someone gets it.