You claim that the first team to lose an inhib loses 90% of their games. While that may be a bit of an exaggeration, I think you're right that losing an inhib puts a team at a pretty serious disadvantage. It's certainly not a coup de grace, however. If your team is slightly ahead or even you can still contest objectives with an inhibitor down. What I've seen more often, however, is losing an inhibitor acting as the nail in the coffin of a team that was already losing, and allows the team that was ahead to quickly seal out the game.
I do understand where you're coming from, however. Being behind (especially as a support main) feels claustrophobic, especially once one of the tier 2 towers falls. It feels like you need shallow wards in your own jungle just to feel safe from getting caught out. This makes it a lot harder to contest objectives and farm the more vulnerable camps like birds and blue.