That's probably due the cost of purchase.

The way airmiles work is the bank buys X amount of points are a big discount from the airlines - then customer redeems it via usage of their card and their bank card points.

But, if people don't redeem the airmiles - the cost per mile will go up thus devaluation. So all these bonus is to encourage us to use the points rather than hoard it.

Maybe UOB's conversion rate is good or their remaining points are limited, so they don't need to bother with giving bonus.

Not MAS fault. They will follow passport name. You might need to change your passport name if that is the case.