I agree with this, but out of curiosity, presumably the funds have their own blockers/SPVs below that they could just route their investments through and allow other investors in the startup to receive the flow-through treatment (like we would in hedge/PE). My assumption was that the standardized governance structure of a Corp was also appealing to VCs who prefer it to the possibility of being screwed by an adverse amendment to the LLCA, etc.
yes this is commonly done in PE but for whatever reason it's not done in VC. usually they say it's b/c of compensation via options but i don't actually believe there is a principled reason behind it.