Its not necessarily the auctioneers. More likely its their clients setting wildly unrealistic reserves in the vain belief their treasured pride & joy is still the rare desirable investment opportunity it was a decade ago.
I do know the % of unsold lots is going up and some auctioneers are starting to refuse some entries because they know they won't sell at the reserve set by the vendor.
But sales of good condition 90s sportsbikes and off-roaders are selling well with strong prices.