Makes complete sense. Small arms are, on the state level, absurdly cheap. And on a self propelled artillery piece, it's not like the weight matters.

In return for this investment, you get artillery platoons and batteries that can self secure against low level rear area threats without having to detach additional line elements (and with the transport to keep up as the guns shoot and scoot) or MPs, both of which are always in demand. In western armies in particular, the prohibitively high cost of a soldier means that any chance you get to not have to spend any more guarding something that might be able to guard itself is going to be taken.

Will they likely survive an infantry company or tank platoon coming through? Nah. Might they be able to beat off a raid by special purpose forces or a squad that got bypassed in the fighting and happens to be in the area? Quite possibly.