why don't people like helicoiled bolt holes in intakes

I helicoil everything. Aluminum transmission case, aluminum extension housing (tailshaft), Indy heads, 440 source heads, intake manifolds of all brands and even a few 4150 carb main bodies. It's not an "if", but a "when". Part of the magic in usong a helicoil is that you have steel on steel at the thread mating surface. This helps mitigate thread damage which is very common when steel is threaded into aluminum.

If you ever went to tighten the last bolt an an aluminum *anything* and the threads started to pull you know that heart sinking feeling. For me it is easier to run through a part and install the helicoils as part of the prep work than to have an unexpected emergency.