I scratchbuild for a few reasons. First, I find there is always a problem somewhere on a kit and that infuriates me. Secondly I'm as tight as a duck's derriere and won't pay what they charge for kits and finally (to keep it short) I don't find it very satisfying to glue a load of pre-made bits together.
HOWEVER…I have several Aerokits models which I am finishing, modifying, restoring and I LOVE doing that, too. Not sure I'd want to start with an unopened kit, although I have always got a kick from opening boxes.
But mainly, with a good stock of woods from wherever and the machines to make that wood into whatever size and shape I need, I can make pretty much anything from scratch. I have done my own research and done my own drawings from that. I make fittings mainly from brass, never buy them, BUT, for this recent birthday my dear wife bought me a set of the old Yeoman/IP/SLEC white metal fittings for the Crash Tender, a model my Dad bought me 55 years ago and which I am finally finishing and I am delighted with them, even though they needed a day's work with files and scrapers to lose the mould lines. They are an essential part of the model and I'm only too happy to have them since some crooked estate agent caused my original blue box of Mersey Marine fittings to be stolen.
I find making stuff so much more fulfilling than buying, but hey, if you can justify the costs you go for a kit if it's what you started off wanting. Personally my tastes are for the kinds of boats that nobody kits, so I have to make anyway, but that's pure chance really.
I simply cannot agree that there's as much work in a kit as a scratchbuilt model if we are comparing like for like. If you want a truly accurate Riva Aquarama Special, you will need to make every fitting as those supplied in the kit are appalling! On my Rivas, there were over 150 separate polished brass parts sent to the nickel platers, all made by hand. If I used castings to repeat vents, they were first made by hand as patterns and the white metal polished prior to painting. All those parts had to be highly polished and wired for the platers. I had to hand paint the floor covering to get the correct colours and patterns. I had to hand draw all the parts that were photo-etched and subsequently polished, wired and plated. The veneers used in the hull had to be selected to appear as smoothly coloured as the real boats (Riva's true skill was in their timber selection for their triple diagonal planking).
Finally, making the steering work from the Cadillac steering wheel via two universal joints, a worm and wheel transfer box and ball jointed tillers was something no kit builder would have to do.
I do think an experienced kit builder could, in fact, stretch themselves to do what I did, but alas, few ever do. That's a pity, but entirely their concern.
Ultimately, if you end up with what you fancied having a model of in the first place, job's a goodun.
Martin