Trade caravans are only bringing food

The first year I had Dwarf, Human, and Elf caravans come by. They all brought the usual items, and I bought some grizzly bears from the Humans. It's been 5 years since embark and now the caravans only bring meat/plants/cheese and whatever I've specifically requested (steel bars, grizzly bears). And now they don't even send diplomats to ask (except the Dwarves).

Why would this be happening? I've given them great trade deals and offerings. I normally buy leather/cloth/grizzly bears when they're brought incidentally, but now it's only food and I'd like more things to buy. Thanks for any suggestions.