What? In my experience the non-greaseable ones are of a higher quality than the ones with fittings. I'd take them any time over the others.
The only ones I've ever had prematurely fail were Moog "Problem Solver" greaseable ends.
Whatever you do, do not drill holes in the ones you have now and put in fittings.
That's my experience too. Especially true for U-joints.
And I would believe this is because the NON Zerk (u-joint) does NOT have the internal passage-ways for the grease to travel.
The OP was referring to Tie Rods. But good point about NOT reworking u-joints.
Back when all suspension parts had zerks, how long did they last ?
Today, 'sealed' (no zerk) is the way to go.