OR because they don't want to invest time or sacrifice in education but that is their choice.
It is because JW believe that their time belongs to God based upon their dedication to God. It would be challenging to take an elder seriously if after becoming an elder and teaching from the platform not to pursue higher education that he went or that he sent is family to college.
I know JW that went to college and then pursued a career and later got appointed as elders or went to Bethel and got management jobs. There are 2 elements here 1. WT discourages higher Ed and 2. Elders and those holding office or positions in the Cong can loose their appointments for going or for sending their kids. It ain't that JW don't want to go, sure they would go and it would be easy for them to pass the courses and make more and easier money. --But they listen to the counsel for the reasons I gave.