Because Glock 48 is a product to make people carrying Glock 19 to buy a new Glock , but glock 43 is a deep CCW product that captures the market where less beefy people found double stacked Glock 26 to be too thick. That's why Glock 43 is thinner and has a way shorter pistol grip.
In the US CCW market, what it matters is the overall height and thickness of the pistol. These things make a pistol print. A long slide is more difficult in Appendix carry, but just a threaded barrel sticking out doesn't get in the way as much as a full slide. This is because what it really matters is the holster size - A glock 48 holster is in general bigger than a Glock 43 holster even when the Glock 43 barrel sticking out.
People with 36" waist line and up ( especially wide people with big guts - not being derogatory here, but body thickness hide the print) may not care the difference between a Glock 26 and Glock 19/Glock48, but for ladies and slimmer people with a waist down to low 30's and in the 20's, there is a world of difference between even a 48 and a 43. Like I said, the height of the pistol grip makes it print. Length of the slide (and therefore the holster bulk) affects appendix carry more. A shorter pistol grip also fits into the lady's purse better.
Thats why there are two different products.
. Hurry!
