It seems very bizarre how we have so many types of doors, yet we don't have gates that are big enough for an XS vessel, but don't cost a fortune to make, and that aren't extremely difficult to find a place to put on a not M to L size ship.
What I'm primarily getting at here is that you can make gates using sliding doors, sure, but they don't have a few major functionalities that gates have. First of all, they do not fold up like the normal gates do. Additionally, making a gate with a bunch of doors means that it cannot be tested for airtightness in the future (when that's probably a thing), due to being different elements, at different angles, and therefore most likely having unfixable gaps. Lastly, sliding doors don't really look that good when it comes to something like a hangar door. The aesthetic they give off is not "this is a super heavy duty airlock mechanism", more of a "I am a thing you push out of the way because I'm a door".
Separate topic altogether, but folding doors, swinging doors, and of course gate-like compressing doors would be pretty cool too. The mor-doors the merrier. Ahem, but anyways, more gates when?