Frequently by midyear, its more like, hey all the bikes of that model are sold out, you have to wait until next year to order whatever they happen to produce.
Its the manufactures which have really turned me off recently. I DO NOT WANT a 27.5" through axle bike for my middle school kid. Yet, outside of maybe a single XXS bike, not a single manufacture makes 26" bikes anymore. So you have the choice, of the sporting goods store bike, or some 27.5" where the geometry is wrong for someone who is 5.5' or so (besides now having to carry a 3rd tire size when we go on family outings, me with my 29" and my other kid with a 26" from a couple years back).
So, having customers walking around with $$$ in their pockets and not having a product to sell is a problem. Particularly, when the answer is "come back in 4 months" so we can check inventory again. In four months, I've probably managed to find another source.
[1] https://www.trekbikes.com/us/en_US/bikes/kids-bikes/kids-hyb...
Kids are not a very lucrative market for the manufacturers or for the bike shops. Hardly any parents are willing to shell out four figures for a bike the kid will outgrow in nine months.
As annoying as that was, as a biker I'm really happy that more people people take the pandemic as an opportunity to discover biking.