That model is more sustainable than aggregators of (say) dog walkers. Everyone found a dog walker they liked through the app, then hired them directly.
The aggregator business model can actually work if you're not greedy. The costs of operating the platform should be near zero once it's built, so even the revenue of first-time bookings, at scale, should be enough to sustain a small but profitable business.
same thing I do with elance - find a freelancer that you like, pay them once thru the app, hire them directly going forward (In my case at the same cost, but the freelancer gets to keep 100%) - everybody is happy, except the middleman. - I pay the same, freelancer gets to keep the fruits of their labor and now I have a happy vendor.
Was looking for a teacher through one of those aggregator websites. Found someone near my location, but the website needed my card details to get the teacher's contact info. Ended up googling their name and contacted them directly.