Why does Mrs Higgins say that Higgins cannot attend Doolittle's wedding?

Stubborn as always, Professor Higgins doesn't rise when everyone else does in order to
attend Doolittle's wedding.  (Doolittle, of course, is Eliza's father.)  From Act IV, here is
what the text says on the matter: 

LIZA. Quite. Is the
Professor coming?

MRS. HIGGINS. Certainly not. He can't behave himself in
church. He makes remarks out loud all the time on the clergyman's pronunciation.

 

The reason on the surface, then, is that
Higgins behaves just as badly in church as he does at the race track.  It is not appropriate, of
course, to correct the priest's pronunciation.  (Ha!)  Higgins always has to interject his own
opinion whever he is, whether it is appropriate and socially acceptable or not.  In my opnion,
this is why Mrs. Higgins is so exasperated by her son all the time.  Mrs. Higgins is a prime
example of an English socialite and is incredibly embarrassed by her son's inability to be the
same.  Therefore, he remains a continual embarrassment to her.

Below the
surface, however, the reason is that Professor Higgins doesn't actually
belong at Mr. Doolittle's wedding.  He has no relation to the bride, the
groom, . . . or the groom's daughter (Eliza) as anything but a business associate or former
"boss," so to speak.  Professor Higgins stands aloof from everyone and, as such,
wouldn't be welcome or even enjoy this blessed event.  So as always, Professor Higgins stays
home stewing about the exasperating events of the past few months with chagrin.