It is an unstable model; if it’s only necessary to hire when someone leaves, there’s no slack - what if someone gets long term sick? What if someone feels burnt out holding the thing up but nobody else wants to hire more - by the time that person leaves it’s necessary to hire more but also late to start the hiring process to find the perfect one replacement and who has spare time and redundant knowledge to train them?
When it will start to make a lot of money, it will do that by having lots of customers, therefore more support requests, more payment troubles, more feature requests, more scaling concerns, reliability and maintenance.
When it starts making money, competitors will notice and may start copying it; relaxing will let them catch up and pass you and take your customers.
There is always entropy, things fade, decay, things need continual “growth” just to stay in a steady state - getting that growth perfectly tuned so it doesn’t grow bigger and need more employees, and doesn’t shrink and wreck the company, it precisely counters the decay, is much harder than growing bigger.
Lifestyle business is not unheard of, some people hit on a great idea and execution and it’s a money printer for them, but it seems that more people who try it either can’t get enough money, or struggle to do everything without hiring anyone until they burn out, or have to hire someone and then have to get more income to pay them and are in growth mode, not steady state.