If I was spending thousands of pounds on a shiney new bike then yes I’d want a proper test ride, but seing as the majority of my bikes are assembled from a mixture of 2nd hand and cheap parts then nope I buy it build it and if I don’t get along with it then I flog it on and accept the relatively minor loss incurred as the price of gaining a bit more experience of what works for me…
I did once take a mate to Cwmcarn for an uplift I was suprised He’d persuaded his LBS to give him a shiney five to test out for the weekend, especially as He’d not really ridden DH and the bike was built up more towards the XC end of things, needless to say he stacked it several times and bent the front wheel, turned out he’d told the LBS he’d just be riding it round his lcal trails… Got the wheel trued up and queitly slipped it back to his LBS, a few weeks later he bought a Reign.
I think the fact that a proper test ride often serves to eliminate a bike from a customers shortlist and it probably won’t get treated with total respect is what tend to put shops off of making test rides so available…