Tri-Rail and Front Runner are both single lines while Metrolink is a vast system, and I am pretty sure that Tri-Rail (like Metrolink) is looking at cutting back a good deal of its non rush hour service due to low ridership not covering the cost.

I'd love it if Metrolink had more service, Marty, but whether you buy it or not, they do not have the money. You can argue that I'm wrong or you can do an internet search for articles on Metrolink that state what I said (which might be more useful and will show you that I'm giving you the straight dope - Metrolink is seriously considering dumping a lot of the non rush hour trains it is now running because it cannot afford them).

I'm on your side, but no cash, no trains.