A couple of reasons ...
I'm sure I read somewhere that W.H. Keith died some time ago - which is a pity as his artwork played a key role in the look and feel of early Traveller editions.
In answer to your question, I think Mongoose should try to find 1D6 decent freelance pen-and-ink types with an interest in sci-fi and some aptitude for concept art. Given that they're based just outside of London
1 they shouldn't have too much trouble finding people.
2 While the sins of the Mongoose art department have been pontificated on elsewhere, IMO the principal one is trying to use continuous tone renderings on a cheap black and white printing process (i.e. using uncoated paper). This never works well - you need to either:
- Go with line art that doesn't depend on subtle gradations of halftones and will render well on uncoated paper.
or
- Use coated paper. Matt art papers will render halftones just fine. However, it's quite a lot more expensive than uncoated paper, and often it doesn't play nicely with hagiographic proceses (i.e. the sort of industrial laser printers used in short run printing).3 Getting good halftone gradations on this type of process is quite fraught as the process squashes the toner out slightly, filling in the halftones.
A caveat with the latter is that even with an art paper, getting tonal gradations from 3D renderings to look good on this stock is quite hard. The up-front cost of colour plates and artwork would be prohibitively expensive to do D&D-style four-colour work in the sort of print runs Traveller material is going to ship in.
Pen-and-ink line art is standard in the comics industry for a very good reason - it's relatively quick and cheap to do (if you're any good at it) and it renders well on cheap printing processes.
Source: Back in the late Jurassic period, I briefly worked as a hack-level graphic artist and typesetter for a couple of jobbing commercial printers. While my lack of actual talent precluded me from becoming the next Herb Lubalin,
4 I did get a pretty good feel for how to make stuff that would come out on a cheap printing process.
1 O.K. Swindon is about an hour from London on the train.
2 There's also that interweb thingy. I hear you can find people on that.
3 I'm not sure what sort of process Mongoose actually uses to print the material but the illustrations in the MgT books I've seen show the sort of issues you get when you try to be too ambitious with your artwork on a cheap printing process.
4 Yes, you might indeed say I avant garde a clue...