Whilst I fully agree with the anti-cheap tools point, it's worth remembering that the ball-end is for spinning them off once you've already cracked them loose. The l-shaped non-ball end is for cracking the fastener loose in the first place. (unless of course they are screwdriver handled ones).
I'm not talking about cheap tools which will then by implication have soft or inferior ball tips. Cheap (rubbish) tools just be avoided or destroyed should they come into your possession. They create the illusion that you have a tool to do XYZ but then at the last moment, drop you into trouble.
I'm talking about grinding them off to reduce workshop error. All of us are sometimes tempted to take shortcuts and these can be to use the ball end on an aluminium capscrew or to crack loose a smalls screw because the alternative of using the other end takes just a little bit longer. In small sizes, the six contact points on the balls are so small that they strip the inside of the capscrew's hex way before you would have thought possible. Then it becomes an extraction, rather than remove exercise.
In your DIY workshop the risk and consequences are small. However, in a profession workshop the risks are significant. I'll give you an example. A customer brought his fancy Cannondale mountain bike in to us for a waterbottle cage fitment. The workshop is very busy but as it is with retail, the customer is always right and the salesperson told him "sure, we can fit this for you?" The salesperson then brings the bike into the workshop and sees the queues. He graps a mechanic's allen key set and attempts to do the job himself. He strips the (stupid) aluminium bolt with his first try. In his defense, just about no allen key can get into that small triangle and his attempt to use the ball side is understandable. Now we are stuck with a customer on the floor, waiting for the 3 minute job, but the bolt is stripped. Now a mechanic is pulled off his current project and given an emergency project. Out comes the dremel. In his haste, the dremel does that zig-zag ricochet thing that dremels do and the chuck grinds a nice dome in the paintwork right into the frame aluminium. Whereto now? A sale of a waterbottle cage now becomes a major drama.
Another example from my workshop. Rock Shox forks have a cable that controls the lockout mechanism. This cable is anchored with a 1.5mm grub screw. I buy each mechanic a nice precision set of screwdriver allen keys but no, someone uses a ball tip in there, strips the screw and now calls on the boss to make a plan. Eventually I saved myself a lot of pain and removed all balls from all allen keys in that workshop. With 11 mechanics and several of them with more than one set including their private sets, it was quite a grinding fest. But I did manage to reduce the number of screws we had to extract by blood sweat and tears.
Yes, a workshop rule should have worked but in reality it doesn't. Off with those balls!