Most of the problem with .22 rimfires for me originate in the bulk packages. When I buy the smaller packs of 50-100 by the brick there are far less duds in them. I also find pistols tend to not strike the primers as hard further increasing the tendency to misfire. If they are put back in the pistol and made to strike a different part of the primer they tend to fire on the second strike, though not always.
Since rimfire ammunition has the primer spun into the rim it is very supceptible to the packaging and distribution process. When you consider that the typical bulk pack is nothing more than a brick of ammo dumped into a box. The tiny fragile rounds are colliding at random and the process is likely dislodging the primer in the rim. You can figure that the primer is knocked about quite a bit.
Take into consideration that the rounds have been jarred around going into a bulk pack much more than the small 50 round packs. Add to that the rounds bouncing around inside the bulk pack as it moves down an assembly line and then being delivered in a truck that again beats the tiny rounds around in their box and it adds up to misfiring ammo.
By way of contrast the smaller boxes of rimfire ammo are not just tossed about in the same fashion as they have to be put into their trays, which by it's nature will not be as traumatic to the cases. Those rounds don't beat their rims and side walls against eachother as they are divided and seprated by their trays. When being transported they are not having as much stress placed on them as bulk packs without trays. I also think that 10 little boxes inside of a larger box tends to have a much better shock absorbing effects. When you compare it to the loose stuff.
There is also the volume of rimfire being produced to include in this tendency. It would be a pretty safe bet to assume that there is far more made today than 40 years ago. With that increase in volume there is a greater chance for bad rounds to get through the QC process. Bulk no doubt is a different production line and it proable they look less closely at those during QC.
Just as others have stated the cost of the rounds are very cheap in relation to the what they cost 30- 40 years ago too. This cheapness results from some cost cutting along the way and ends up showing up in the form of duds as well.
It is frustrating to get misfires in the ammuntion, but that is to be expected in rimfire ammo. I get very few so long as I avoid the bulk packs. They seem to be the real culprit in my own experience. IMO bulk packs offer no savings at all when they tend to cost you in lost rounds overall. It adds up in the long run.