Publishers and distributors to blame for piracy
For those who can read Spanish, this is what Playstation Spain says about the game. For the benefit of those that cannot, this is the crunchiest bit:
[...] Ico will be again on sale in February, to coincide with the [European] release of Shadow of the Colossus, and to please those fans who wish to enjoy this sensational game themselves. The bad news is that this title, of infinite sensibility, did not make many fans in Spain, so it won't be re-edited in this country. But if you can speak English and are curious about it [...], it may be worth it to spend a bit more and get an import copy.
I could talk for ages about the problems for monolingual Spanish people to speak English, but that's not the point. I could also talk about the problems there are in Spain to get hold of console games (PC is infinitely more popular)--my brother was telling me how Mario Kart DS was sold out in lots of places, and it seemed the re-stock may take a few months (if it takes place at all). I could also explain how current games (and consoles) are much more expensive in Spain, and how ordering a PAL copy of ICO will be not easy to get for less than 75$. But I won't... today.
Spain is one of the countries where piracy is most common in the world. It's part of the picaresque, I guess, and part of the culture--if we can get away without paying, we will. Of course, they can blame on the popularity of pirate copies for the limited releases of games. However, it is also true that they do not make it easy for gamers to get legal copies. As it turns out, the second-hand market constitutes a very, very small percentage of the Spanish videogame market. There are also very few specialized shops, and only in the largest cities.
The other problem is the choice, which is also very limited. My brother told me a couple of months ago how he went to FNAC, the main entertainment store in Madrid, and they only had 5 games for DS. 3 were the different versions of Nintendogs, which at least is a relief, because they were not FPSs or driving/sports simulation. RPGs have a really bad reputation in Spain, after a two notorious cases of murder related to table-top RPG and Final Fantasy VIII. So basically, there is not much to choose from, even if you're affluent enough to buy the games. What can Spanish gamers do? You can try import, but the generally limited second-language capacities of many gamers, and the general reluctancy to online orders make that an exceptional choice.
There's also the problem of translation--gamers expect games dubbed in Spanish (there was a petition for the dubbing of MGS3), which increases the cost of the publication of games. So gamers are to blame for this as well, and sometimes they get what they deserve--the infamous dubbing of Halo in Mexican Spanish is an example.
I guess that, as long as Spanish gamers are treated with this contempt -- refusing to release a great game in Spain, even if it is a European release -- Spanish piracy will continue thriving.