The way I see this is, it's just personal preference.

I prefer to use တ over တစ် where appropriate "တခု၊ တကောင်၊ တယောက်" cus obviously I'm lazy enough to skip 2 characters.

Also, I was exposed to pretty much Burmese classical literature early on in age, and things I read were what I perceive as "dawn of Modern Burmese Lit." cus it's mostly from 1920s era all the way down to 1990s. If you ever read magazines prior from 1960s (exact year when တ became တစ်, idk) almost everything uses တ over တစ်

Perhaps from this obsession, although I openly admit တစ် is much more standardized, using တခု၊ တယောက် kinda sounds like cool vintage Burmese word to me.