The NCAA rules allow for one year, renewable scholarships. This technically means that any player can be dropped from a team year to year. Now even the coldest and most cynical of coaches and teams (like Saban) don't just cut players who underperform. They usually encourage transferring or find some medical excuse to get them off the team but still receive a free education.
Making something formal that we already practice doesn't seem like a big leap. BC should do it for the PR advantage and for recruiting purposes. We sell the BC experience and the BC education. Offering a four year scholarship just reinforces that position.