Yesterday I was on an IFR flight about 50 miles from destination. The
area was getting covered with TS, including my alternate 20 miles futher
west. Home base was 150 mi to the east. I realized I might have to
reverse course to escape, but did not have enough fuel to get home for sure.

So, the last chance to land before the TS got heavy was coming close.
When about 15 miles from this new "alternate" I told controller I wanted
to change destination. I expect a vector to the final, and I was needing
to start descent. Nothing happened. Finally when maybe 5 miles out, and
way to close to get a vector, controller quizzed me with "I need to know
what is the reason for the change in destination??"

From the tone of voice I could tell I caused him a problem. The traffic
was not heavy. I have never had anyone question a change like that. When
over the airport VMC opened up briefly, I cancelled and landed.
Wondering what might have caused the query.