I’m not sure that’s always true. We have our own homegrown adserver that’s almost 100% context based (a few ads for stores do rudimentary IP geo-targeting, all purely first-party though), and it does well with both banners and text based ads. It’s in the digital photography niche. I’d assume generally places that are strongly oriented towards a niche can do a lot with context based advertisment. CTR is much better than for Google ads (that we also run).