What is the point of HD Terrain?

I like it although it has some drawbacks. The realer the reality the realer it really looks is my motto. Although most of my time is spent creating extensions to my layout I do like to drive and experience my efforts in the first person. So I'm all for it with the proviso that it doesn't strip my Mac's gears. What I would like to see amended in HD are the same deficiencies as others have mentioned - a more generous dollop of textures per baseboard and more finely sculpted cuttings and embankments. Incidentally I see the latest update now feathers the 'paint under' results rather than leaving a hard edge which may be a small step for Trainz but a giant leap for Trainzkind.
When HD Terrain was first mentioned and all the virtues and demos showed us great stuff, I had hoped that this could be applied to specific areas rather than whole baseboards or routes. Imagine using HD terrain for cuttings and other locations where the cliff-edge or riverbank need that kind of detail while other places on the same baseboard don't need it such as the city center nearby.

Like many things we have with this program, it's an all or nothing with rarely anything in between.
Why HDT? Because people asked for more realistic terrain and better shadows. The narrower cuts and fills are visible from the cab.

People want more textures, but that affects performance and how much space is used on hard drives. Already people complain about how much space is used when converting to HDT and it does take a lot of space. But it stores a lot of data.

They tried allowing the routes to use a mix of terrain, however the routes ended up with weird artifacts at the borders between the baseboards and that problem hasn’t been solved that I know of. People don’t understand the 5/10m grid file format has weird artifacts. The old gnd file is easy to decode but the edges between the baseboards are weird. No idea why either and no help. HDT doesn’t have that same artifacts, but no help there either. HDT is more efficient for graphics processing as it uses a single pass vs multi pass of 5/10m terrain and automatically changes amount of polygons processed depending upon distance. So having different terrain resolutions may not be necessary, except for space savings or large routes.

Plus store page with features HDT, etc
Already people complain about how much space is used when converting to HDT and it does take a lot of space. But it stores a lot of data.

About 16,000 more data points per 10m grid than the 10m resolution uses and that data has to go somewhere. Just prior to the release of HDT the compression level used to store data was significantly increased, partly, I am sure, to accommodate these extra demands.