Checks only addressed to him?

Ditto what everyone else has said! For my own sister's wedding I made the check out to her hubs to help them avoid any weird bank issues.

A lot of people do not open a joint checking account until after marriage. Or always keep His, hers, and ours accounts. If addressed to include you, they simply are making sure it can be deposited and used 24 hours later. Which means you can do them all in one bank visit to either account. We do not often give money at the time of a wedding. Usually, if giving money, we send it in advance of the wedding. And sometimes it has sat for 2 months to the wedding, then weeks after. Because we made it out in both names, and the B and G were holding it thinking they were not meant to cash it , or waiting to open a joint account, after the wedding. Now we make it out to one person, with a note, please deposit this and use it, if needed, even before the wedding, or to reserve things for your honeymoon.
I don't know why they do not both sign it and put it in whatever account they have. But 1 name, a few weeks or more before the wedding, it always goes through the bank immediately. They have it to use, and we hate outstanding checks.

I only ever write 1 name on a check. I don't know if people have joint accounts and if it would cause issues cashing it or not. I wouldn't stress it, especially if everything else is addressed to both of you

I doubt it's the you not being good with money. Honestly, it's probably the easiest way they can think to minimized you getting upset if they did assume you were taking his name.

They are probably thinking it's easier to cash a check when it's just written out to one individual....I know i always second guess how to address a wedding check.