I told you, it's because Blake got into bed with Bolt, and if one goes down they both go down, and there is NO WAY that t&f will let Bolt go down.
Like others have said here, the only reason anybody still cares about the sport is Bolt. It's too bad, because t&f is pure as a discipline. We want more complexity now, more dirt, more "entertainment".
Bolt will NEVER be caught, and likely neither will Blake, and if Blake is ever caught, Bolt will be long gone by then.
A partial solution, as others have suggested, is for the IAAF and other federations to give the athletes to run more often, and more competitively--that is, so that there are more head-to-head matchups among and between the big names, which creates rivalries. Take the 100m, for example--not everybody can be nails, every time out. Finishing orders will be shuffled, positions will be distributed among the top athletes. Meets should invite more, say 16, to fill out 2 semi's, and one final.
Can you imagine if, at this point, Bolt was revealed to have been doping? What would happen to t&f?
I honestly don't know if it would be good or bad, in both the long- and short-terms, but I'm pretty sure the powers that be think that it would be bad...very bad, and therefore it will never happen.