Digital radio allows for far more efficient use of spectrum than FM
I don’t think Switzerland is crowded enough to have 10x more radio stations sustainably.
So the way to use it more effectively is to build more transmitter stations at a lower power, but at that point you're competing with cellular networks which have access to probably 10x the spectrum and already have a load of infra built out to support that.
For example, if you used FM for LTE/NR it would be completely congested 100% with even just signalling overhead of the time apart from very rural areas (as suddenly everyone's phone that has no service because of being out of the reach of any mast suddenly gets it - perhaps because of thick walls etc).
Similar if it was used for WiFi - the transmit power would have to be so low to avoid interference it would have no benefit over current spectrum (2.4GHz doesn't work in most places for this reason).
And rural areas already have starlink - which has 2GHz of downlink frequency alone (plus they can add more somewhat easily, which is impossible for FM).
Also there's often going to be a lot of interference from abroad, 100Mhz signals while VHF can carry far under the right conditions.
All the pirate stations back in the day were ultra high power AM stations operating out of Mexico.
Around here, following the digital switchover, most people could no longer receive all stations, but which ones depended on exactly where they were. And those that can be received are of exceedingly low quality. Very heavily compressed and relatively low resolution. But each station now provides multiple streams.
On the positive side, that did help me finally stop watching TV entirely!
In my country DAB has station dedicated to playing classical music, jazz, youth-oriented pop music, current affairs, religion, rock music - not to mention dozens of local radio stations!
FM allows for only a very limited number of stations, which means it ends up in a bidding war between the large commercial stations - who in turn have to play fairly generic music to attract a large number of listeners. With DAB there's plenty of space left over for niche stations, as they can transmit essentially for free.
Especially licensing. Even on commercial radio you can regularly catch them playing "10 second" clips of different songs, to stay within fair use, that they wish to play but cannot legally do so. The college stations are more brazen about it and will flat out tell you that they can't play different jobs for legal reasons.
Indeed, commercial radio does have to appeal to an audience, but that audience would unquestionably enjoy other music – at least within the same genre. But playing it for them opens up a huge legal minefield. It is a lot easier to pick a small catalog that you can properly audit and disallow anything beyond that.