The chemistry thing is true, and I think they like having a taller, more reliable shooter as opposed to the 3 6 foot shooting guards masquerading as points. But I think the biggest reason for no Cleveland trade is that they have absolutely nothing else to throw into a trade. As much as teams are looking to dump salary, they're not going to dump All Stars unless they get cap relief AND young, cheap talent. Teams want the KG trade (cap relief and young future All Star like Al) or Kidd trade (cap relief and young All Star Devin Harris) not the Pau trade (cap relief without any real potential stars, just Marc Gasol).
I think the Gasol trade provided that much of a lesson to other GMs who didn't want to be this year's Chris Wallace, even in tighter economic times. We are pretty fortunate that nobody wanted to repeat that trade, since Cleveland just did not have the cheap, young talent to throw in with their expiring contracts. If they had that young talent to include, Cleveland would be one actual All Star better right now.