There are a few good reasons why some people engage a main contractor rather than sub contracting individual work themselves. It costs more, but for good reasons.

Imagine an AC with water pipe running to next door toilet drain, with a route under the floor tile. Say got leaking and suspect from cracked pipe. Want to re-hack, re-do piping, re-screed, re-waterproof and finally re-tile. If one maincon, he will be liable for the whole thing. If different subcons you self engaged, good luck to find one that will own up.