You literally get what you pay for:
Axminster have what ought to be* a good system - their responsibility end-to-end, and people placing the product who are familiar with it and have a personal interest in making sure it's delivered properly, in the right place, without damage, etc. From the customer's perspective, that means no finger-pointing ("it was them, not us!"), etc., and far more help when the item arrives. The drivers meet customers face-to-face, and I'll bet they feed back their experiences into the 'system' too - that sort of interaction is really valuable in terms of understanding the customer (what proper marketing is all about).
If Axminster changed nothing else except that they sent out half-empty lorries, for a faster delivery, the cost would be much more, which they'd have to pass on as a direct charge. If they didn't, soaking-up the costs in the rest of the business would make that part less competitive (higher overheads).
I'd guess they've 'run the numbers' to see which - owned delivery vans or couriers - is better for their business. Couriers, even the best (and we all know they're very variable), would cause their returns cost to shoot up and customer satisfaction to drop.
With the possible exception of explaining more clearly on the relevant web pages that some delivered items may have delayed delivery, I'd do it just the same way they do. And no, I wouldn't give a courier option, either: the costs of running two options would be huge (returns rate woiuld skyrocket, for a start).
Just my twopence worth.
E.
*I'll admit I've never bought anything big enough from Axminster (yet) to need their delivery service, but I've set up similar processes in another industry, where in some circumstances we specified that we delivered/commissioned products ourselves (and wouldn't drop-ship or let customers do it), to avoid costly mistakes. So I do understand the issues.