If you look at the last few years canon has typically released 0 EF "non-L" lenses, ~1 EFS lens, but 3-4 EF "L" lenses per year over the past 5 years. Just looking at that, it seems that canon is trending toward EFS lenses a little and EF "L" lenses more significantly.
It looks like the most recently released EF non-L prime is the 28/1.8, in 1995. That roughly coincides with the time that zoom lens quality started getting sufficiently good that zooms were seen as useable lenses that could produce good quality.
The most recently released EF non-L zoom appears to be the 70-300/4-5.6 IS, in 2005. That is the only EF non-L zoom released since the EF-S mount was introduced, and of course the real benefits of EF-S come on the wide end anyway.
I'm not sure they need a new inexpensive general purpose zoom lens with an EF mount. In the past, everything was full frame (i.e. film), so with 35mm Rebels available, there needed to be consumer options for lenses, too. Since there are no 'cheap' consumer-level FF dSLRs, the need for inexpensive EF lenses is not that strong, having been supplanted by the EF-S line.