I think you answered your own question. As you say very few players invest and so only those players who are also DMs and have therefore purchased tokens will know that they can't use those tokens whilst joined to a game - they can only allocate them when they create their own campaign; create the character and then import into the DMs game.
Allowing players access to assets is highly problematic given the way that Unity handles assets. Portraits are allowed because they are differently set up and created than are tokens or images.
If you look around the forums you'll find plenty of historical posts looking for FGVTT to have 3d maps and assets. Such posts will often be people wondering why FGVTT is 'so far behind' the shiny Foundry which has lots of 3d stuff but not a lot else. So I think the 3d upgrade is essential for FGVTT to attract new customers. Whilst there may be a lot of posts from people who aren't interested in it we don't know exactly just how much new business it has brought in; and the people who shout the loudest are often those with complaints. Most people who like things don't ever bother saying that in a public forum. Given the number of questions that I see about how to do this or that with the 3d asset building both here and on Discord it seems to me that a lot of people use them and so like them.
I agree that the forums aren't well used like they were in the past (Discord has probably been responsible for much of that); and it's the same people who regularly post. And since it's a microcosm of the user base the opinions tend to be skewed towards that small group. Smiteworks don't just rely on what is said here or on the feature lists alone; they monitor a broad spectrum of sources to garner what both existing and new customers want.
There are several requested features on the feature list which have been completed and some that are currently in progress.
