if there junk why are miners including them in blocks?
to get the fees
the TX themselve are probably all junk tho.
Actually, at levels like 0.2 - 0.3 btc per block, fees too are junk yes. Hence the presence of 0 tx blocks.
Personally I'm currently mining with -blockmaxsize=0. My connectivity is not that good so it'd take me a couple secs to upload a full block and then it would take some extra time to propagate, so I can't risk losing 25 btc for peanuts.