I often worked the first hive I got with no veil, shorts, t shirt, and sandals.

It was several miles from my home, and I was lucky to get the opportunity to work it once a week.
I thought that as long I moved fluidly, didn't bang around and used common sense, I'd be fine.

The second year I kept bee I did quite a bit of splitting, and encountered bees when they are queenless -- and discovered even bees from "gentle" stock can be pretty cranky when queenless, as I got stung up pretty good that day.

As long as the weather is clear and sunny, you get in the hive at mid day when most of the foragers are out, there is no thunderstorm coming, the bees are genetically disposed to gentleness, you don't drop anything and startle them, don't accidentally crush a bee and release alarm pheromone, don't use too little smoke, don't use too much smoke, don't use the wrong kind of smoke, don't still have habanero oil on your fingers from slicing peppers even after washing, don't smell bad to bees, don't use scented toiletries, didn't just kiss someone wearing cologne or perfume, and don't any-one-of-a-hundred-other-things, you can often work bees without a veil.

My bees are nearly always gentle.

But today I opened a hive whose queen quit laying a couple weeks ago.

It's a very crowded hive, well populated for the flow, and is supered.

I had placed a new, caged queen in the hive previously after looking (unsuccessfully) for the queen.

After four days, I'd checked on the caged queen and there were a lot of bees biting on the cage, so I knew the original queen was probably still present.

I was out of time, so I left the new queen cage (corks had not been removed) in for the night.
If I'd had queen excluders with me, I'd've put them btw the three brood boxes, but I hadn't any with me.

Thunderstorms prevented me returning yesterday.

With thunderstorms forecast for this afternoon, and all day the next few days, I wen back up to pinch the original queen today.

Unfortunately, the bees had had enough time to chew through the cork in the queen cage, and the new queen had been loosed. Hopefully the new queen survives, but it is not likely based on the behavior of the bees when I was in the hive last time.

But here's the point of all this:

These normally very gentle bees had
a) been in a hive that was entered a lot more frequently than normal lately,
b) been queenless long enough to have no open brood,
c) were opened when a thunderstorm was imminent and the barometer was dropping like a rock.

These normally gentle bees (descended from the gentle queen in my original hive mentioned above) were very aggressive, head butting, veil-obscuring, stinging my gloves, and when I was through, pursued me for 75 yards after I had finished.

That's totally out of character for that hive.

If I'd relied on their behavior up til today, and if I didn't know from experience that the conditions present were likely to result in an unpleasant hive, I might have worked them in shorts, or just a veil.

And I'd be in bad shape right now.

Until you are experienced enough to be able to watch the hive entrance for a moment and have an idea of what's going on inside, and are able to recognize when bees are likely to behave more aggressively than normal based on condition, you're not wise to work bees without your skin well covered and a veil on.

You may never have an issue.
But if you do, it's not likely to be just one or two little stings.

Be safe.

Have fun
Enjoy your bees