I'll try to answer with the extremely small amount I know.. My Brother Flies, and I can go a bit by what he says.
In the old days, there were planes and Copters.. Planes required skils acquired to fly, copters even more so.. Now there are cheap ready made quad copters, that are much more stable, much easier to fly and as such many more folks are getting them. It is leading to increases in regulations and community no fly zones etc as towns and such try to find a way to deal with the latest craze of folks flying something over people and places taking video.. Invasion of privacy complaints etc.
To expand a little more on this....
Like ron said, in the old days it took you quite some time to fly...you started with an instructor...he was tied to your radio with a system called a buddy box....they are still used today....if things get crazy the instructor can flip a switch and take over your plane. It would also take you all winter to build the plane, and if you crashed light, a few days to weeks to rebuild....and if you "re kitted" it (crashed hard) you are out a great deal of money, effort and time. As a result of this you had people that flew that really knew what they are doing, valued their models very highly and would not risk them. If talking about a heli take this X10.
Today I know people that are flying quads that can't fly....if you turn off the GPS they have no clue how to get the quad back. Add to this there is no buy in anymore, you are not spending hours and hours learning to fly, and months in building something....it has no real value outside the few hundred $$ you spend to buy the thing....so people do stupid things with them.
Now add the FPV or cameras in general (they are different) and you get people with no investment in what they have flying in places they should not trying to get a video of the nude sunbather in her back yard....or flying off buildings in a downtown area....or flying around full scale aircraft.
Because these people have no investment in this hobby, they really don't care...and now we get laws about having to register and all this, when for the past 40+ years we have had zero issues....and those issues are created by these jack wagons that just don't care about the hobby....it is a fad to them.
So guberments do what guberments do....they go after the items and not the jack wagon that is actually doing something wrong....and as a result they punish all the people that have done things correctly for decades....and those that actually cause the problems....nothing for them, they will not comply or they will just quit playing with their toys.....this is what I mean by ruin of the hobby.
It is so stupid that my 40" wingspan P-51 is the same in the guberments eyes as a DJI Phantom...I actually have an F4 Phantom as well so I don't want to get that confused.
Hope that clears things up.
I want to add....
I don't want to come across as anti quad...I am not, I own 3 of them...and a few more in boxes not built.....and I enjoy the current crop of ARF/foam planes on the market....they are just great planes.....it is this RTF with zero training that is the issue....add to that they will actually fly all by the GPS and that is a real issue.
What really shocks me is that no one has used one of these things for a terror attack....I think it is coming...program it 10 miles away and let it go....and that will be the end of the hobby....I am shocked things are still the way they are with the quad issue involving Merkel
All that was needed on that quad was some kind of small bomb or bio agent and it is all over....and my hobby, something that I have spent over 30 years doing will be no more....and I will have idiots that don't care about it one bit to thank for it.