It really isn't all that similar; pet names are unique, aside from the few remaining doubles, and can make a lot of difference in value, no matter what the pet actually is. Pets' names have sentimental value, and because they're unique, they make for much bigger and more long-term goals.
Items' names, in contrast, give no telling of how valuable people will find them. It's the item itself, not the item's name, that people want. Looking for a certain item is more comparable to looking for a pet of a certain species and colour. You know that, unless you're looking for some super-rare item or Creatu like Cooking with Fire in Reiflem or an albino Credit Shop pet, it's only a matter of getting enough tu to buy it. Thus, there are far less long-term goals to get certain items than there are to get certain pet names.
Besides that, it would make the game (Dah. I lost The Game, by the way. x3) nearly impossible. There's no way to really sort items by what they are, so the only ways to order them in a search would then be by name, by price, and by who's selling them. Thus, items would be even harder to sell than the average pet, unless you have a particularly well-known shop. It would be nightmarish to try to find anything without either knowing someone who's selling the item you want at that time (and even then, you have no idea if you're getting the best deal) or knowing the item's exact name.
Many merchants would be mad, and many newbs would have immense issues getting the items they need or want, while older players may still have problems completing personal collections and whatnot. No one wins.
Gah. Ranty. o3o