Hi,
I want to know why chromoly frame are not galvanized to prevent rust? or am I wrong?

They are. Check out the Sanchez at Swobo.com. Flat bar fixie with galv frame.

Thanks for the link. Do they galvanize the inside of the tubs?
Why not do it on every chromoly frame?

Tubes! I don't know but I intend to buy one and I'll let you know...or give em a call. I have their Otis series which is aluminum. The sanchez model is always sold out.
Its expensive and environmentally unfriendly to do so....which is why most chro-mo frames are not galv'd.

A quality paint job and powder coating is just as effective if it is taken cared of. I have a 17 yr. old Basso Lotto road bike with the paint still looking like showroom.

Hehe, you are more then welcome to show your Basso here.
What is a powder coating ?
why not paint inside the tubes?

Powder Coating is a painting process which uses an electrical cathode (frame) to anode ground application of sintered powdered paint to electrically adhere to the metal. Very reliable and long lasting.

I don't know whether galvanized cro-mo steel has this problem, but I have a bike trailer made from galvanized steel electrical conduit and where the conduit has been scraped, the galvanized layer apparently came off, because the steel rusts there. So high quality paint may be just as good.

Correct. Galvinizing is only a surface treatment to ****** rust. If surface is altered, rust will appear.
Although it does last quite a long time.

They don't paint the inside of the frame because it isn't necesarry, and for those who feel it is rustproofing works fine. Obviously you can put inside the frame substances that would rub off, etc... on the outside but are fine on the inside.

Some builders (e.g. Scapin, Basso) claim that the inside of their steel frames are chemically treated to resist rust. If this isn't the case, I'd just use some Framesaver or similar.

Yes. J. P. Weigel's Framesaver will protect the inside of a steel frame, and paint or powdercoating will protect the outside.