Focusing on flipping of houses would be more profitable than waiting on rent. Actually, selling houses is a business, and shouldn't be a one time thing, the money generated from selling one property, can erect another one, which can still be sold. All the same, a rented house wouldn't raise enough money to build its replica in a short time. Therefore, the owner is not interested in selling houses, but wants a stream of income that doesn't ask for his time anymore.
you are right, that selling a house or apartment will get a lot of profit and more instant than renting it. However, sometimes people who rent their houses do not want to sell their houses. they choose to live in a new place, but still want their old house as an asset and investment. So, what they do is rent out the house they own. it will have at least two advantages, the first is that their house may still be maintained by someone else, the second is that the assets they own will have a high price every year.
If we want a return on capital in the near future, it will indeed be better to sell the house that they have built and that's right, as you said, there are some people who choose to rent and they will be able to be patient in terms of return on capital, but over time, if the house is well maintained, of course the price will continue to increase and also this is more profitable for them and make the asset an investment for their future is also good However, they must still take good care of their house so that in the future it is still worth buying at a high price because the house is still livable.
When we choose to rent, of course we have to occasionally keep control of the house and if indeed the tenant does not take good care of the house that we rent, then it will be better for us to no longer continue to rent to them so that the house we have is damaged or there will be many things that must be repaired after we rent to them.