Common mistake. People put things on hand-tight and forget or neglect to torque them properly. This is why it's imperative to always use a torque wrench on every bolt you wrench.

Fun story, had this happen with a new truck tire when I was a kid. The shop put the lugs on hand-tight and didn't torque them. About 5 miles from the place the front wheel came off the truck. We were coming to a stop, felt the front lurch and scrape and there she went free rolling away.

Another fun story, I'd taken delivery of an '08 Husqvarna 510smr from a reputable dealership as a racing platform. Going through my engine brake in I noticed all 4 front axel pinch bolts were backing out--those are installed as part of PDI. The shop and I had a pretty frank discussion about that one.... we were cool but that was a serious f-up on their part. Those pinch bolt were also Locktite free, wtf.

Finally, if you ever let anyone else wrench your bike, you're well served hitting any bolts touched with a torque wrench a second time just to make sure.