Why are 1,3-diols protected with aldehydes but 1,2-diols are protected with ketones?
Let's look at the protection of a typical 1,3-diol with benzaldehyde and acetone:



The theory is that the formation of the six-membered cyclic acetal is less favourable with acetone than it is for benzaldehyde, because with acetone you cannot avoid having one methyl group being axial.

The next-most stable thing after a six-membered ring is a five-membered ring, which can be formed by the protection of a 1,2-diol instead of a 1,3-diol. So, acetone happily reacts with those 1,2-diols to form five-membered cyclic acetals, whereas benzaldehyde is more selective for 1,3-diols since it can enjoy the stability of a six-membered ring.

When there is a choice, like in glucose, you get rather different results:



However, I am not sure how much this principle extends to protection of compounds with only two hydroxyl groups. I am guessing it should be possible to protect 1,3-diols with acetone too - after all, a methyl group is hardly the worst axial substituent to have.