It's hard to be excited when your physical copy will eventually become the world's tiniest paperweight because Rockstar didn't feel like spending a little more money on putting all three games on the cartridge. 

In 20 years these games will be rereleased again, so game preservation of these games doesn't matter that much. If you have it downloaded it doesn't matter wether the eshop it still running on the Switch in 10+ years or not.

I don't care about buying the games again in 20 years. I care about the games I'm (not) buying right now. 

What about the patches ?

This is the issue with modern consoles in general. They make it impossible to backup anything. The WiiU may have failed as hardware but that let you backup all your save files and patches etc to an external HDD.  Even if I went all digital, the games are tied to your console, so if your console dies so do the games if the online service is shutdown 10 years later and I cannot redownload them onto the new one.

There is a reason why a lot of Nintendo retro games go for big bucks now because Nintendo gamers are collectors first and gamers second. They are proud to own and hold their games. Even here in Aus, when Wii had the most sales in Aus compared to PS3, there was still way more PS3 games in second hand stores than there was Wii games.

The sooner these idiot 3rd party companies realise this concept with Nintendo gamers the higher their sales will be. I have passed on so many games on Switch simply because I had to download one of the games, or half the game etc. Why can't they just use smaller carts and more of them if they haveto spend money on the larger ones? Charge me more, i'll pay it if the full content is on one lol.

Now I have played all those GTA games before on my PC so it isn't like I desperately need to play them again. But you know what it would have been cool to have them for my Switch in my collection

First, unless we are talking about an outrageously buggy or glitchy vanilla version, you can still play the game without patches without a problem. Second, patches and DLCs are something that cannot be made any other way (mostly). So when the eShop says sayonara, we won't be able to access that content. It sucks, but it is what it is.

Another story is a company having the choice of putting the whole game on the physical copy or put part of it behind a download. That is something I cannot tolerate. Because if I'm paying for a physical copy of a game I want THE physical copy, not just a piece of it. When I buy a DLC or download a patch, I know that the only way to get those is via internet, so if I'm interested in those I have to accept those terms. Unless they make a physical release for the DLC, in which case, that's the way I'm going (like Xenoblade Torna).

I'm still amused by how silly sounding this game title is.

Grand Theft Auto: The Trilogy — Definitive Edition

Why couldn't they have come up with a better name than that? Could have been:
GTA: The Definitive Trilogy

Would have sounded better and eliminated a "-".

Among Switch owners I know there actually is a fair amount of buzz, just like there was for Skyrim back in 2017, a similar situation where a massively popular game(s) came to Nintendo and a handheld for the first time.

Personally I can't stand GTA but there is definitely excitement among plenty of Switch gamers.

Well I don't know about your consoles, but when mine sees a patch is available, it usually refuses to launch the game without it.

OR Grand Trilogy Auto: the Definitive Theft Edition