Theres many issues with this, but the one i'm going to bring up, is this:
Royalties (and other profits obviously)
Now, blizzard lost alot of money through starcraft because of the LAN function, due to the ToS etc etc it wasn't really all that necessary for tournaments to comply with any rules blizzard may state because the hardware its using is all your own. So alot of the korean tournaments didn't really generate a great deal, if any profit for blizzard despite that being the games only replay value in this day and age.
Next, comes Dota. Fantastic. The only real reason that kept me playing WC3 for as long as i did. I liked the campaigns sure, but did they and the skirmishes have unlimited replay value? no. It got old after the first play through real quick. So dota, and the endless other "melee" maps that came out kept me entertained until the expansion, and the next series of campaigns came out.
Dota, is now a game, infact its 3 games. By different companies.
The man who took up the reins, icefrog coupled with this own team made LoL or Dota 2, whichever one, and 2 groups of fans made up heroes of newerth and whichever one of the titles icefrog & co didnt make.
Now thats a lot of profit to be missing out on, considering the original creation was played on their servers, by their player base that they massed.
In this day and age of patent disputes and endless copyright agreements, blizzard seems to have taken the view of any security conscious administrator. Its locked down, until they say otherwise. DRM is probably just the beginning.