In the same way as .tv is for Tuvalu.
If Catalonia has its own TLD, why not California or Maine? If it's a català tld, why doesn't brezhoneg get one? Or cymraeg? Or võru, saami, euskara, söl'ring, cemhuî or ajië?
Politics.
Catalan is spoken in these regions: (spain) Catalonia, Valencia, Mallorca, some of Aragon in South-Eastern France a town in Sardinia (Alguer / Alghero) Andorra (a small country)
For the rest of cultural/linguistic TLDs... have they asked for one?
You may want to note that my comment had two clauses, and that this is handled in the second one.