Could there be a clearer match for "good old games" than the Infocom catalog?

Some of the other games are included in the Zork packages which are on GoG. Planetfall anyway is in the Zork Anthology. Not sure why some of the other games aren't here though.

Yes there could be, and yes there is, but otherwise having old text-only adventures would be a very welcome addition indeed.

I guess the problem is that there probably isn't that much interest in those, so they really wouldn't be topping the sale charts. Then again, they don't need much tweaking to get them working, and file sizes are almost zero (even with some modern launcher apps), so there is no real downsides about them either.