Joe Public would generally by default want to go direct.
but what
is direct?

The most direct route? (e.g. Glasgow to London is via S&C then GNER from Leeds) or direct trains (not always available, and sometimes slow/impractical e.g. Poppleton to Leeds)?
"Not Doncaster" can be "direct", and I once witnessed someone be told off for using such a ticket on a through train, although he wasn't charged the (roughly £1) excess.
It's a common belief that direct is what people want to do, but IMO there are 3 groups of people, 1) those that want the
cheapest, 2) those that wan't the
fastest, and 3) those who want to go some unusual route for some reason (e.g. visit friends/family on the way, or for some other reason).
And, while we're on the subject of 'Direct', some tickets are routed 'Direct', yet there is no clarification of what exactly that means in the Routeing Guide. One example is Hartlepool to York. No direct trains since the NT/TP split, and the shortest route is technically avoiding Thornaby, but obviously you have to go via Thornaby. But can you then go into Middlesbrough (permitted as Thornaby is a member of Middlesbrough Group)? Arguably, yes. The ticket probably should be routed "Not Darlington" to avoid confusion. Also, one (former) guard claimed that such a ticket is not valid for a GNER train between York and Northallerton, which I fail to see why - as Northallerton is on the direct route. I think there is a strong case to say that "Direct" means anything permtted in the RG except for mapped routes (ie, direct trains, the shortest route + routes within 3 miles of shortest), but it'd be useful if they clarified it!