Why not?
Does any of the forgotten realms content have guest passes? I haven't looked for a guest pass since.... well I've never looked at them. Not that I dont like them. They are a great way to introduce new content to people.
The problem is never how to get new, innovative thoughts into your mind, but how to get old ones out. Every mind is a building filled with archaic furniture. Clean out a corner of your mind and creativity will instantly fill it.
Dee Hock
I would assume because they want people to buy it, not have their friends GP them through it.
Anál nathrach
orth’ bháis’s bethad
do chél dénmha
Excellent question. I can imagine several good answers, but if guest passes are worthwhile source of revenue for Turbine then I think they should be asking this question. If guest passes have instead proven to not be a decent source of revenue, then that's probably the answer right there.
I can be found on Orien as Cilon
HC7: Typhoon, Dreaded Knight, and Wish. HC6: Naivety. HC5: Who Is Here. HC4: Cylon Centurian. HC3: Soulstone in Your Pack. HC2: Carnage