The first obstacle to the draft is the law. There's a cap on the maximum amount of military personnel, and right now, Congress has authorized a temporary expansion beyond that number. Temporary. That means, in order to use the draft, Congress would first have to raise the limit, and that brings us to the next obstacle.
Money. It costs 1.2 billion for every additional 10,000 soliders.
But, what about retention? It stinks, so that's why we have to have a draft to replace them. Wrong. Retention is pretty good, and so is recruiting. Read articles if you like. Retention bonuses tend to cost less than training new folks to a replacement level of experience.
The military has reserves it hasn't even called on yet - the Navy has the Fleet Reserve, which is folks who retired after 20 and before 30 years of service, and are actually receiving "retainer pay" instead of retirement pay during that period. The Army has something similar. The services all have the Inactive Reserve, made up of all of those folks who served their initial active enlistment but still have time remaining on their eight-year committment. See, each enlistment is eight years long, with part of that time used by active duty and the remainder being inactive reserve.
The Air Force and the Navy are scaling back, and the Navy's doing it on a pretty big scale. If Army manning was so bad that they'd need a draft, well, hey, there's a whole pool of trained people to recruit.
Quality. Most military recruits have at least a high school diploma. Drawing on statistics (and I detest statistics) from the coursework I've been doing, nearly 30% of high school students never attain a degree...so would that 30 percent be ineligible for the Draft? Does anyone else see failure becoming a viable option for people to avoid being drafted? We need to work at educating the population better, not at giving incentives to remain illiterate.
I remember when the Navy instituted a two year active duty program. By and large, it sucked, because the folks came in as general duty sailors - that means they were over the side painting the hull, they were cleaning up down in the engine rooms, they were serving chow, and they were doing just about every other bit of manual unskilled labor out there. They didn't receive any advanced training unless they decided to obligate for more, so they never experienced the best the Navy had to offer. What incentive did they have to perform well or to remain in the military? None. Does anyone give their best under these conditions? Not really. And they were volunteers, so I really don't want to meet people doing the same types of jobs when they didn't volunteer.
Well, it's time to go to work now, so I'll get off this soap box with a final comment: The mostly unsupported draft bills are either a scare tactic in use for this election period or are the product of deluded members of Congress who have no understanding of what the military requires or desires.