1) Basically the same reasons as must for wine http://en.wikipedia.org/wiki/Must
. You need the juices and oils out there being fermented by microorganism and gradually oxidized. Loosely compressed, weakly rolled cakes will tend to age like maocha, and loose maocha ages about as well as oolongs do. You'll get some, but it's nothing like optimum. That's why you see 70's loose maocha relatively cheaply compared to the bings.
2) Well, because lincang teas are totally a scam. Has nothing to do with the actual qualities of lincang teas, but because tea traders can get much bigger margins by buying cheaper lincang maocha and selling it at higher prices, oftentimes as Bingdao or Xigui or whatever the latest hype is. In practice lincangs probably could age pretty well; some of Xiaguan's famous cakes probably has plenty of it along with Dali, Baoshan, and Wuliang leaf. Some Dayi could be said to have lincang as well. However, they won't age as well as something with a great deal of Banna leaf. What does that mean for the collector? I'm perfectly willing to buy, say 2002 Tai Lian, which I *think* is mostly lincang. I'm perfectly willing to think that my nice JingGu teas will age pretty well. I think those things because they are really, really good, and will hold onto and elaborate many of their flavors as they age.
Just because anything north of Banna won't age as well as Banna leaf does doesn't mean that they are not worth aging. It does mean that you have to have higher standards to buy lincang or lancang leaf, and a higher willingness to take losses if they don't work out. For example out of a number of aged Jingmai older than 2009 I've tried, only two, a 1998 Evening Fragrant Jade that costs like a thousand dollars at Bana tea, and a sold out HeShiHua 2001 Jingmai from Sampletea has amounted to very much. You want to reach for as high a quality as you can afford, if you want to age Jingmai, and you should still expect it to be somewhat hongcha after about seven years.
About the competition? There isn't one. Banna is totally, absolutely, locked down. Anything truly good is insanely expensive (and unavailable), and those farmers there know it. North of Jingmai, the ancient tea groves are much smaller. In practice, there is very little great JingGu, Kunlu, Bingdao, Xigui, various Da Xue Shan, etc out there. And much of that top stuff never enters the market, not even for those $300 Bingdao cakes. There is just not that much great lincang out there that you'd want more than a relatively comparable banna tea. So most lincang you see out there is touted to be better than it really is.
It is better if you take the time, get to know how to drink tea and taste a few older examples, get those puerh-legs underneath you, and scrounge in the bargin bins for forgotten stuff.