I've only had one bar with a grease hole for the tip sprocket... it was the only bar I've ever greased (still have the little grease gun thingy)... and it was the only bar I've ever lost a sprocket bearing on (shrug)
I've seen a few others go bad (three if I'm rememberin' correctly)... every one was running used motor oil for a bar 'n' chain lube (shrug)
I've never lubed a drive sprocket (or clutch drum) bearing either... never have lost one... and every one I've ever had off was plenty "wet" enough (shrug)
Likely, at some point in the past, there was darn good reason for greasing such things... but also likely, metallurgy has improved, designs have improved, lubricants have improved, and the understanding of how they relate to each other has improved. Still, no matter how well designed and maintained, "stuff" does fail, especially things that move and/or get hot... it-is-what-it-is... and that's why we have "servicing dealers" and "parts departments". After all, the larger "pro" bars do have "replaceable" tips correct?? I see that as a concession that "stuff", in fact, does fail... it-is-what-it-is (shrug)
The sprocket tip bearings on both my Stihl bars have never been "dry" from use. How do I know that?? Well, I've flushed them with solvent and compressed air until they were "dry" a couple of times (checking for "play" in the bearing) so I know what a dry bearing feels like... they've never been "dry" from use, if anything they're over lubed during use. Still, if there was a grease hole in one of my bars, and the manufacturer recommended greasing... well, I'd grease it I reckon... but I certainly wouldn't sweat it if I forgot or ran out of grease (shrug)
To lube, or not to lube??
Do whatever makes ya' feel all warm 'n' fuzzy... it likely don't make sour owl crap difference either way.
Heck, some guys wash 'n' wax their saws... some even lay them on the pillow next to 'em at night.
Me?? I just blow the thing off with compressed air and toss it under the work bench out in the non-climate controlled shop (shrug)
*