Why are IPS officers not interested in joining CBI ?

There was a time when IPS officers were keen to get posting in CBI but now the situation has changed. If sources are to be believed, presently the agency wants about 50 SPs but till March this year only two IPS officers - Veer Singh and Manoj Singh -have applied. Similarly , against  12 vacant DIG posts, the  agency has received only Nihal Singh's application till the said date.