tl;dr: most feedback on twitter ads assume it is intent driven (i.e. google adwords), when in most cases it is not.
IMO, it's the root of many social companies struggle to monetize with ads. We've been spoiled the last while because we knew what people were looking for, and could promote directly against that. In some ways, social ads are a step backwards from this.
I agree. In some ways social ads are a step back from that, but only because you establish contact with your customers much before they have needs that you can satisfy. So the time to first sale is a lot longer.
But I think, on the flip side, the relationships you develop with them are a lot stronger and a lot more powerful. The problem is, it's very hard to back that up empirically because it's a lot more complicated than just measuring CTR.
This is why Facebook's new retargeting is pretty exciting (disclaimer, I'm a cofounder of a company in the space, http://perfectaudience.com)
Facebook has/had the same issue: huge audience and targeting that just didn't capture intent. By opening up inventory to folks that have that intent data, retargeting companies, Facebook's able to "sell umbrellas to people in the rain" to use the lingo of OP.
It's going to make a big difference for them in the longrun and we anticipate Twitter doing something similar in the near future.
IMO, it's the root of many social companies struggle to monetize with ads. We've been spoiled the last while because we knew what people were looking for, and could promote directly against that. In some ways, social ads are a step backwards from this.