Even if we consider one-shots that were pilots for hoped serializations, the share is small; and it is tiny for one-shots that were not intended as pilots. However, an example of the last would be Kase-san; so it happens.
i imagine they still got paid a decent amount being featured on here, so maybe if they expand the 'universe' of this world/story that's fine versus just using it for their next series
(seems to be their only work as far as i know, be amusing if they only did it as a hobby and did like a one shot once a year as opposed to working a 'regular' job the rest of the time) Artists might be more 'respected' in JP but i don't think i've heard of like them talking about that career having good health benefits/insurance, then again i guess that's just a better thing overall in JP whether you're an office worker or just a konbini cashier but that's tangenting sorry
Edit: nevermind guess i was thinking of a diff artist, this artist seems to be the one who made' my yandere gf won't let me rest in peace' (didn't know that before making my initial comment i was just basing it on the cover lol)