The current demands in their life. No matter how well you know someone, there could be something going on in their life that would make the calling overly difficult that you don’t know about. It also shows respect to the person you’re extending the calling to that care about whether the calling will create an undue burden.
The spirit of this practice is D&C 6 (“studying it out” first in order to get revelation)
I’ve never seen this practice come across as awkward or be anything less than appreciated by the recipient.