Random encounter are necessary as mr_planescapist said to make the world alive.
Everything is too static in BG3. No time, no night, no one moving, no one coming/leaving, ... This world is all but alive.
There are way too much random encounter in WoTR IMO but too much is better for immersion than nothing.
They assume separated instance for (mini) camps, which is already really really bad and Immersion breaking... they could eventually add instance for random encounters when we fast travel... It would be an awfull solution like it is for camps but it would still be better than nothing.
But not for the sake of it.
Pathfinder WotR has them and by and large they are a waste of my time. Easy opponents that cause me nothing but time in a loading screen. Yes, the odd interesting character etc... but it is only tolerable because with RtwP it's quickly dealt with. It's usually harsher when you are camping as you are often tired and without heals, then it can be nasty.
I appreciate it is more in keeping with BG as a series to have travel and random encounters, but with the migration to TB combat, I would only add in random encounters sparingly. That does not mean you could not have areas that on different playthroughs have interesting encounters within the same area. Not the best example, but Diablo 3 had quite a few encounters that sometimes appeared in specific areas on different playthroughs. Most of them were tedious, but it did add that element of randomness.
