The reason for this is obvious commas and periods are absolutely essential to context and communication while question marks are rarely if ever needed

I mean lets just see what a happens when we try to communicate without commas or periods lets just try it and see the chaos that results

Imagine a shopping list without commas bread eggs milk potatoes utter complete confusion

The wise designer of todays instant message keyboards understands that people primarily communicate in assertions declaratives and imperatives while questions are exceedingly rare

And on those rare occasions when one needs to ask a question the sentence context always makes the question clear without need for a question mark

lets consider some simple examples

no

This sentence is clearly a question

yes

This sentence is clearly a statement

There you see our wise designers decision to slavishly follow traditional keyboard structure is more than jusified

well done wise designer