Number of reasons:
- superb light wind ability
- masses of lift, ideal for jumping & boarding
- huge amounts of pull, great for scudds & buggying (watch the lift though)
- great build quality
- very fast, responsive, and quick turning for a 6M kite (thanks to the rif-raf that tucks the tips in)
- very smooth power delivery, feel the power coming in, nice for timing jumps etc.
- excellent value for money (£325 for a 6M)
- individual colour schemes, many and varied
- it's different (at least it was, but everyone seems to be getting one now)
- the more you fly it the more you get out of it, you learn to fly this kite over time and this makes it extremely rewarding
- you can say "I'm just getting my Bego out" without getting arrested...
I'm sure there's more, these are the ones that spring to mind