It is quite true that the Lycoming and Continental operating instructions are probably largely influenced bt liability, and who can blame them for that! Also true that there are many factors which affect the circumstances of a cold start. I am certainly guilty of cold starts for my O-200, and it went through it's last overhaul with no related damage at all.
That said, if owners who are only modestly informed of all of the factors, are thinking to repeatedly "do their own thing", which conflicts with the mfg's recommendations, simply for convenience sake, that's not something I would support. There are lots of "tricks" and half measures which will get a cold engine running, and I'm not relating them here. There's a proper way, and it's clear. If you can't do that, come as close as you can. If you regularly fly in conditions for which a preheat is obviously appropriate, arrangements should be made to provide the required heat. If it's an occasional, unexpected circumstance, then yes, the engine will probably tolerate it a few times.
I don't expect the engine manufactures to invest more effort to further clarify the information they have already presented, with respect to preheat. If they were to do all the research, and sell an STC for "this is how to really cold start your engine", would people pay for it, and happily return the manufacturer's investment in research?
I hold STC's for changed process only for aircraft, and people still try to do it for free!