It may be something to do with customer requests? If they had a high volume of them then surely there would be a bit more.
I think more businesses are geared towards emails and desktop pc's than doing things on mobile apps in any case... It's kind of a niche area I guess.
Personally and at work, we use a mix of courier services and a mix of website and email depending on if we have the specifications of the goods on hand or not.
Would be bluntly honest in saying too that i'd prefer to work this way than trying to do this through say, my phone as I just feel it would ultimately be less productive. There is nothing that stops me either from logging onto the website via my phone and doing bookings if need be.
What I would love to see... Is a courier company that really does have a functional website and services within... Still looking for one who has got things right as theres pros and cons between all of them but ultimately it is not ideal.