Some anons are not getting it. Yes, POTUS can give SOTU in his little Oval Office, or in a letter,
BUT, the purpose of giving it in a large Presidential type venue is that
most of the Democrat and Republican Leaders are present, the top Military Brass are there, the Supreme Court members are there and media.
The public can see the faces and action of the politicians LIVE and see how they react to the POTUS and great news of our country.
Pelosi would be standing behind the POTUS where Ryan did last time.
It is priceless and POTUS looks glorious.
If it is in a small office, or letter no one will see it.