I think this is for higher level contact - not personal friendships. Networking for professional development - more along those lines.
Something I need to get back into. Interacting, at least casually, on a routine basis with a wide amount of people has lead to every job I have ever held - they came to me based on my reputation or past interactions. It's definitely the best way to get a new (and better) job rather than blindly fishing for them.
That's the real power of systems like this. Not to develop personal friendships, but to remain relevant in the eyes of a large number of people so that if they have a future opportunity you will be top of mind for how they can get it addressed.
I think it's why he stresses making the contacts personal and with meaning/value specific to that person. These aren't soulless automated computer generated emails, but a system to prompt him to write relevant and sincere contact messages.
Is it a lot of work? Sure. But building up a network of people who see you as contributing value is priceless.