Every single MS-4 wants to pursue an "academic" career (including me, when I was in that position), if they know "what's good for them." In other words, the current training environment is heavily slanted towards academics as reflected in the admission criteria. Yet, each year 40-60% of graduating residents go into private practice so there is an obvious disconnect.
The question you should be asking is not, "why are 'academic' programs pushing their residents into private practice," but rather, "are academic programs where all/most residents go into academics preventing their residents from going into private practice?"
At some programs (which will remain unnamed), there is a heavy bias towards academics. So much so that residents are actively discouraged from going into private practice and if they do, the department "blacklists" them. At other programs they have a much more enlightened approach. Although the expectation is that you'll go into academics, the faculty bear you no ill will if you don't.
The reasons for choosing private practice > academics are numerous:
1. Better compensation
2. More flexibility in location of practice
3. Don't have to deal with academic institutional bureaucracy
4. You can publish at your leisure, rather than "publish or perish"
Personally, I was born to do academics. MD/PhD from an MSTP, research was Rad Onc based, went to a top residency and did Holman, yet I went into private practice. I could go into the reasons why, but the "tl;dr" version was that I wanted to stay in a competitive market more than I wanted an academic career. The major academic centers in the area weren't hiring so I took an awesome "hybrid" position and have a volunteer faculty position.
For a variety of reasons the majority of graduating residents gravitate towards private practice. I'd argue that this has more to do with the individual and less to do with the program.