Switzerland is also very small, as countries go. The longest train route is IC 1 (St. Gallen <-> Geneva) going from the (almost) easternmost point to the westernmost point, and it’s 4 hours (it does have a few higher speed sections close to Bern). They simply don’t need much speed if they run frequent and reliable trains.
And the Swiss railways operate high-speed trains for those links with neighbouring countries- their routes to Milan, Venice and Frankfurt use trains capable of 250 km/h (ETR610 or Giruno), though they only travel at 200 km/h within Switzerland.
