At the end of the year Rindt signed with Team Lotus as joint number one with Graham Hill. His first year at Lotus was marked by a scary accident during the Spanish Grand Prix where his aerofoil collapsed, resulting in a broken jaw and concussion. Luckily he was able to recover quickly, although he had some vision and balance problems for some time afterwards. While recovering from his accident he wrote an open letter to the press calling for a ban on aerofoils. He believed that aerofoils had nothing to do with motor cars besides being dangerous to drivers as well as spectators.
http://www.ddavid.com/formula1/rindt_bio.htm
For reasons like this, the regulations strive to ban movement and maintain a high level of safety. Personally, I also agree.
It would be cool if there were moveable aero devices, but safety comes first, and until the engineers can design something that can truly be 100% safe under the pounding and rigors of racing, well, we just can't risk funerals for drivers or anyone.
Besides, these days we can make the cars as fast as we wish. In fact, many regulations are in place to contain excess performance. Heck, just allow 2 liter turbo powerplants and crank in tons of wing, allow fat slicks, and lap times would drop dramatically.