IRC is a different use case. There are no gaurantees that your needs will be addressed. Help through IM had less benefits for "learning". Also IRC particularly shines for niche frameworks where the knowledge is limited to a few that really want to share it into a support community. But for something like Rails, you're better off following tutorials and blogs. But then you can get overwhelmed and connect the dots wrong. So guidance through pairing can fast track learning on time and resource sensitive projects.
In my experience, IRC rooms tend to converge on a state where they are really useful to a largish coterie of experts that frequent them and know each other, and frightening, off-putting, or actively hostile to the newbies that this project is targeting.