Typical houses are built on the LAMP stack, not Rails. A lot of configuration and many of the conventions embodied are Rick 's and Rick ain't around. There are lots of corner cases built into any structure, and clean quick and straightforward pricing models by necessity come with lots of caveats. There's often a reason a light switch needs replacing that's bigger than just swapping out a part. The old one is still there because replacement was nasty work.
Throw a retail model at this and people expect refunds just because. I no-shit-know someone who had no problem taking back fresh from the ground annual flowers to Home Depot at the end of the season for a refund. The fact that new waste pipes won't work that way is why contracts matter. Good plumbers are busy and paid well, Amazon can't Uberfy them. It's not a commodity skill like driving a clean late model car. Sawzalls are involved and expert experienced judgement is required. They'd do better with web developers because they would nit have to solve the locality problem.