There are a number of practical reasons that no 10-300 will ever be made. Most "super-zooms" have about a ten to one range (30-300) and they trade image quality and other things to get that much. High end zooms typically have a zoom range of only 3 or 4.
Its hard to get even average image quality as the zoom range goes up. Too many engineering tradeoffs.
With a wider zoom range, you end up with a big lens, because a 300mm lens is going to be about 5 or 6 inches long even if its a very slow lens (F5.6 or worse). If you try to make it a fast lens, say F4 or F2.8, then in addition to being long, it will have a huge diameter. This has several downsides:
1) big lenses are expensive
2) big lenses are clumsy
3) big lenses are hard to hold still
If you want a 10mm lens, or even a 10-24mm lens, you expect it to be small and easily handled.
Since the existing EF 28-300 is nearly $3000, and a 10-300 would have to be more expensive, who would want to spend $4000 or more? No professional that is for sure, and that is way more than a consumer would want to pay.
DLSRs allow changing the lens easily and quickly. You will be a lot happier if you get three lenses, 10-22, 17-55, and 55-300