Here's another reason why.
In Eph. 4:11, the first three occurrences of "and" in the NASB 1995's list of leaders is the same Greek word (de). But the fourth occurrence of "and" (the one between "pastors" and "teachers") is a different word (kai), which is perhaps best rendered by a hyphen ("pastor-teachers").
All pastors are teachers, but not all teachers (like me) are pastors!
C-ya!