Canonical is now offering the 32-bit of its Ubuntu operating system, either the LTS or the regular one, as default, but this might change soon.
Ubuntu has been recommended for the 32-bit bit architechture for a long time. Even the word on recommended was present on the official website until not too long ago. A proposal has been made to make the 64-bit architechture the default one.
“I would only propose that we default to recommend 64 bit on the Ubuntu website for 13.10. The biggest item pushing us there is that newer machines will need 64 bit to work (EUFI). Ubuntu server (13.04) already defaults to 64 bit only (unless you manually go to releases.u.c),” stated Bryan Quigley on the official mailing list.