Historically the central government has extracted money and resources from Catalonia. Catalonia was one of the first regions in Spain to develop its industry and definitely the strongest on that: https://es.m.wikipedia.org/wiki/Revolución_industrial_en_Esp...
These days it is widely accepted that the Catalan people send 16 billion per year to Spain that are never returned. That wouldn't be a problem if it wasn't because our infrastructures are underfunded and only around 35% of the budgeted investments were actually executed: http://www.elnacional.cat/es/politica/estado-ejecucion-infra...
But this is not just an economic grievance. The issue is way more complex and includes (but not restricted to) language, cultural and respect issues.
Edit: This comment is now at 0. Please argue instead of downvoting. You're breaking HN's rules.
What? You totally can, at least in most countries, as long as you can prove that your wife did something wrong. Can Catalunya prove that Spain did something wrong? Yeah: Franco.
http://www.vozbcn.com/figura/2009/11/20091127nou.jpg
"Shouldn't your wife be allowed to divorce from you if she wants" with an implicit (because you abused it) would be, on the other hand, an extremely rude example. I don't think that this passive-agressive possibility was even in the mind of the people posting it.
The true fact is that I can't divorce from my wife without her permit and she could not divorce from me without me agreeing to sign the divorce papers. Does not match the case of one part splitting unilaterally. A better term for this case would be marital abandonment, and a even better term would be family abuse. There is not such thing like a "right to desert your family keeping the house for yourself only".