A likely reason is because these users do not own a PC (or any equivalent) to access these games. You can read up on papers about emerging economies and mobile internet penetration rates on sites like pewresearch, but a tl;dr reason is that smartphones and data plans are cheaper and easier to access in recent years and so we're seeing a large number of new internet users from emerging economies that do not own PCs and yet are still active on online spheres.
Lag in gaming is a relative issue; you experience lags as 'lags' because you have a PC gaming experience to compare to a mobile gaming experience, whereas some users have only ever gamed on mobile devices meaning that your 'lag' is their par for the course.
Another possible reason is tablet gaming. Like another user said, its more portable so if you own an android tablet you can work it in the bathroom for more privacy I guess?
While the reasons above aren't comprehensive, I hope this explains the situation a little