Historically, there have been four reasons to host the games:
1. Our national ideology rocks! Examples: Berlin 1936; Moscow 1980; Los Angeles 1984.
2. OK, we lost the war, but we’re back! Examples: Rome 1960; Tokyo 1964; Munich 1972.
3. We’ve graduated from the Third World! Examples: Mexico City 1968; Seoul 1988; Beijing 2008; Rio 2016.
4. Let’s have a party and attract some tourists and foreign investment! Examples: everyone else.
The problem is that the Olympics have become so expensive, #4 has become harder and harder to justify, and the other rationales can only work under very limited circumstances. As a result, unless the costs can be reduced or the profits distributed differently, you may start to see the Summer Games exclusively in authoritarian Third World countries with an image problem and lots of money to spend.