What's the purpose?
 

If this has already been answered I apologize. I haven't been here for awhile.
What is the purpose of moving the players away from the basket at the lane during a free throw? I notice they are doing it in high school now.

Too many players in the lower spot were being pushed under the basket.

You can get the official take on the nfhs web-site

They wanted to give a defense and advantage to get the rebound.

Peace

"You are correct, sir," (Ed McMahon)
 

From NFHS:
FREE-THROW LANE SPACES CHANGED: During a free throw, all players will move up one lane space, leaving the two marked lane spaces closest to the end line vacant. A new mark (2 inches by 8 inches) must be applied to the lane line near the free-throw line to designate the last 3-foot marked lane space. This rules change may reduce rough play during free-throw situations while maintaining defensive rebounding percentages within an acceptable range.

Acceptable Range is: B. Lane Positioning. There has been much debate on what – if anything – to do with lane positioning on free throws. Some want rules that would move players up on the low block or even eliminate the first-lane space. The belief is that the players underneath the basket are at a rebounding disadvantage. Data collected from a variety of sources does not support that belief.
Multiple studies show players in the first marked lane space garner approximately 75-80 percent of all free-throw rebounds. That is a range the rules committee finds acceptable and is consistent with historical norms. The team closest to the basket is supposed to get most of the rebounds, not be guaranteed a rebound. The rules in that case are also not designed to give each team an equal chance at securing a rebound.

Man, it sure seems like more than 20 - 25 percent of the time in games that I see.....

As others already pointed out - it is to reduce rough play on rebounds. This is one of the best rule changes in the last 5-10 years ... especially at the men's college level!