mature markets end up 3-5 competitors because further mergers end up blocked. capitalism would otherwise allow them to contract to a single player. So I'm sure that's one government control that you'd agree is worthwhile.
Sometimes you do see more, and it's indeed because regulators are stopping mergers. The airline market is like that. But it's a mistake and the regulators should back off. It's not helping people to have a gazillion undifferentiated brands, at some point it's just wasteful duplication.
The idea that every market would contract to a single player if not for the benign wisdom of the regulators is a trope. Regulators are tiny compared to the number of markets that exist, but competitive markets aren't the exception, they're the norm. You see it even in very sticky locked-in markets where regulators deliberately decided not to intervene, like operating systems and browsers (Justice Dept effort to break up MS was cancelled).
There are very few markets that are both natural monopolies and stay that way for long periods of time. Outside of things that tend to be owned by governments anyway, like road networks, I'm having a hard time thinking of any.
Whilst pure monopolies are rare, my impression is that surprisingly many markets consolidate to an oligopoly, and that this reduces competition and is generally pretty bad for the consumer.