Which brings up another important distinction... does the person you're making the suggestion to already KNOW the higher-level language in question (such as someone familiar with C on a PC, but never touched a microcontroller before), or are they learning programming in general at the same time they are learning the specifics of programming on a microcontroller? In my mind, this also makes a big difference in what language they should start with.
For someone who has never programmed at all, assembly may seem daunting, however because it's the "official" language of pics, and there are dozens of books and walk-through guides out there, it's not a bad starting point. Trying to learn a language and the hardware at the same time is not necessarily a great idea, because it's easy to make both functional/syntax mistakes in the language, as well as mistakes related to how you're using the hardware. For what it's worth, ASM at least involves a rather orderly, logical flow, as long as you're not doing anything horribly fancy, and it's not hard to visualize what is happening at each step. It is harder to follow when the program gets huge, but for beginner projects where they're just flashing an LED or something, it should not be hard to visualize and follow what is going to happen with each instruction line.
I'd much sooner suggest to someone unfamiliar with both the language and the hardware to learn the language an easier way, like spending some time with C on a PC, and some time learning the hardware with ASM on a PIC, and then try putting them together afterward.
For someone who's already proficient in C on a PC or otherwise, I'd probably be much more inclined to suggest that they jump to C sooner, though a little while spent in assembly would still be a good idea.
And just like Nigel's been saying, the support for higher-level languages pretty much sucks. You can go to bookstores like Borders or Barnes&Noble, or a library, and pick from a number of different books on PIC programming in assembly... But there's not much out there for C or BASIC or other languages on PICs, and I think this is because for the most part, the compilers are third-party products that haven't been around that long, rather than a standardized language set by the manufacturer that's been around for a long time. And, the compilers that are more of a professional product (like Hi-Tech PICC) generally end up being made into increasingly expensive commercial products (such as close to $1000 for PICC). Who's going to write an entry-level book about a compiler hardly any hobbyists can afford? And who's going to write a book about a compiler that is free or cheap, but is still in development and isn't perfect and stable and isn't guaranteed to continue being worked on? If you think about it that way, it's still too bad, but it isn't all that surprising that the official, supported assembly language is the focus of most books.