There is multiple reasons. Some tracks simply didn't had overhaul for long time, so, it's needed in order to keep Grade 1 certficate. Abu Dhabi repair made to make race more interesting. In Spa they build new stands to accept more spectators and also make changes to held 24 hours moto race.
In general yes, changes in tracks allows owners to accept more type of racing and offcourse earn from it. Though, overhaul isn't cheap thing, it will took some time return ivestment.
I mean racing was never something to make money from that easily, most of the teams make a loss if you look at F1 teams, but they still do it, it is a bit about marketing as well. Secondly I feel like track owners were exception to this, they didn't look like they had too much cost, I mean sure they have some, but not like teams at least, it is just track, but if the overhaul is too expensive, then considering how much they make, it must take years before they make a profit like you said and then it's once again getting closer to doing it all over again.
If we assume it takes 7 years to ROI on that investment, and you need to do it every 10 years, then it is only 3 years of profit. This is of course making it up without any numbers, I am just guessing to calculate how profitable it is to own one of these tracks, maybe it is not as profitable as I assumed.
