The other absolutely glaring "apples-to-oranges" point to be made is that there are very strict plumbing code standards that need to be adhered to. If I go into a house to put in a sink, there's pretty much one way I can do it. If I get hired to build an app, there are a limitless amount of combinations with which it can be built and deployed.

If I'm coming to fix a sink, I have a pretty good idea about how it will have been done. That's not the case for fixing a bug in an unseen codebase.