Cuz branding, I guess. Honestly not sure.
You could always do the classic /s to denote sarcasm.
My wife was telling me the other day that people have started putting tonal notes in brackets. For example:
(sarcastically) Do you even OWN any rare games?
Honestly I don't mind the above approach. It achieves something akin to a novels narrative style, eg. "I'll tell you where you can put that egg!" Jonas guffawed while gesturing to his rear.