The reason bike dealers are going bust is very simple:
There's not enough people buying bikes. Bikes are mostly non-essential luxury leisure purchases at a time when the cost of living is impacting sales,

I suspect that statement requires a bit more clarification, Will. Some bikes do seem to be selling well & the couple of dealers I have used recently have suggested that sales are holding up. But the bikes that are selling appear to be from the "disruptors" at the lower price end of the market - to the extent that some popular models are on back-order.

I have had various suggestions for this, but there mainly seem to be two streams - some buying smaller lighter bikes due to advancing years and others giving up on expensive PCP deals for top end bikes & choosing to buy something cheaper outright instead.

Bike sale profit margins are very slim and dealership overheads are very high.

And one of the major drivers of the "high overheads" is the ludicrous requirements of the importers / distributors. The last local dealer of Japanese bikes gave up when the importer wanted them to spend £10k on re-tiling the showroom floor with "corporate" floor tiles only available from them. The dealer had not made £10k profit from the franchise in the previous year so just gave up and concentrated on second hand bikes.
Another dropped Piaggio and Suzuki & downsized premises due to the unachievable sales targets required. They had previuosly dropped Honda after being fined for "infringements" after an inspection - £1k per "infringement", which included having a non-franchise branded coffee cup on a salesman's desk, a cracked floor tile under a heavy bike center stand leg and a dusty mark around a ceiling heating vent. Another Piaggio dealer apologised for the lack of stock on display, as they were in disagreement about being expected to pay more for a bike than it's retail price and being told to "make up the difference on servicing".

Some companies were "empire building" multiple franchises & locations on unsustainable finances.

Some still are - Vertu for one locally. I know know nothing of Vertu's finanacing, but if / when they go under there will be a mainstream manufacturer dealership desert around here.

I suspect there are other drivers as well - the mainstream manufacturers seem obsessed with pushing unuseable performance levels from ever larger capacity and heavier bikes that are not relevant to public roads and charging ever more for them.

KTM & BMW seem to have really screwed up with reliability and their "head in the sand" responses to sorting issues out. BMW's pannier debacle - they fall off, apparently & the official "fix" for those who don't want to return them for a refund is to use luggage straps to hold them on. No replacement product until the middle of next year according to the German magazines - and this from the maker that all but wrote the book on functional, capable, integrated luggage in the '70s / '80s. Some latest BMW models seem to require mandatory swapping of the (expensive - €900-ish for the part plus fitting) driveshaft at a certain, relatively low, mileage level.

KTM's camshaft woes seems to a be a text book example of how not to handle a recall situation - deny there is a problem, force customers to pay for expensive repairs that use modified parts, deny warranty claims and then cave in to the inevitable and have to sort it out. Plus their dubious ploy of supplying some bikes with all the options working only for them to stop doing so after a month unless you shell out another arm and a leg to turn them back on again. Parts supply seems sketchy too according to some reports of parts taking months to arrive.

Personally I would trust BMW and (particularly) KTM as far as I could throw one. As KTM have taken over distribution of CF Moto bikes, I would be wary of them too - great having a 4 year warranty, not great if every warranty claim is "declined", or the bike is OTR for months due to parts supply issues.

The Japanese manufacturers seem to have largely gone to sleep, pushing limited ranges of long-in-the-tooth models with crappy paint jobs, not great finishes, miserly specs & shorter than the "disruptors" warranties for high prices.

Servicing charges for the mainstream bikes at franchised dealers are positively eye-watering - major services well into four figures reqularly quoted in the Comic. Tyre prices are high and life very short compared to a car - any small savings I might have made on fuel commuting by bike before I retired would have been more than swallowed up in tyre and servicing costs compared to the car.

Interesting times - I suspect things will get a lot worse for the trade before they stabilise & I doubt they will ever recover to earlier levels.

NIgel B.