I think it is $imple. It is about money.
The special pioneers are probably no longer considered to be an allowable expense for religions by the taxman. This has to do with restructuring to fall in line with "religious exemption" tax status. The special pioneers too closely resemble a "workforce" which, of course, the WTS does not want to be responsible for or have to pay labour costs on.
The new and improved jw..org will emerge with a clergy class, a smattering of missionaries and have the look of all other religions.
Huh. I wonder when they will open convents for the women.