There are gels that come in squeezable plastic lotion-style tubes, e.g Bulldog.
For the others, I wonder if it's partly a customer expectation thing? Back when I was using cartridge razors and shaving foam I would shop by visual pattern-matching as much as the label, or to put it another way, I wouldn't even have looked at gel in a tube, because I expected all shaving lubrication products to come in a can. I hope that makes sense? It probably doesn't because my last coffee has worn off
That's about how I see it too. In my view, the gel would be best, and much more handy, in a tube (like shaving cream or toothpaste).