The company I did a bit of work for did everything themselves but someone else surveyed and priced the job. It's another variation on the same problem though - too many differing interest involved when it should be the customer dealing direct with the contractor.i do bathrooms and kitchens for a living ,done loads of wetrooms .the problem with theses company's is that they dont do it all the sub out the plumbing ,then the electrics ,then the tiling ,then the plastering .even the painting ect .bottom line is there are to many people involved ,and they all blame each other .i do the lot myself ,and have a very good customer base . the other problem is people will go for the lowest quote ,then moan when they get a crap job .
I've built houses and run the job on my own as a bricklayer, using trusted subbies I've worked with before for the other trades and it's worked liked clockwork. But it's one person in charge, one person dealing with the customer, one person organising the site. And a customer who doesn't keep moving the goal posts and who trusts me to get on with it. That's what you need for a smooth job.

.