Why are the boiling points of aldehydes less than those of ketones? Both aldehydes and ketones have a carbonyl group, but since the carbonyl group of ketone is between alkyl groups, wouldn't it be more difficult for it to form hydrogen bonds than aldehydes? Why then, do aldehydes have a higher boiling points than ketones?
It isn't that good a generalization: always look at the data first.

Here is a table of most of the aldehydes and ketones with 6 or fewer carbons (the labels are used in the chart later):



Now plot this on a chart:



Branches is the number of branches in the carbon chain.

Note that while for 3 and 4 carbons the ketones do have higher boiling points, it is not clear this is true for 5 carbon compounds and certainly not true for 6-carbon ones.

So, I'd argue the pattern of boiling points is complicated and there is no simple pattern that needs to be explained.