That's my point, it makes no sense. Gear = damage. Especially since it depletes rapidly you get more damage from filling it as fast as possible.
the idea that one mob = max gear or anything even remotely close is total nonsense tbh.
Hell, without showtime it can take up to 90 chain hits to max gear.

It's not like no one cares about mobbing dps or like there are no situations with only bosses and no mobs. Though tbh I dunno why mobs matter at all in this case, I don't know of any mechanics that refill gear faster if you kill a mob or something.

And in the first place the difference between max gear at 7 bars and 2-6 bars is 20% so unless you are at full gear you lose a ton of damage and not just proportionally a little bit.
Without Showtime at lvl 10 you substantially decrease the chances of reaching 7 gear bars and staying there for the duration of your pas and are a lot more likely to just stay at 2-6 gear bars getting at most the 10% gear damage buff instead of the 30% one.

It's very basic math, it's just that the exact numbers depend on a number of other factors as well so no one really quantified gear importance like dpp or something.