A manga service that limits what devices you can use it with is garbage. It's a set of static images than can be read by any device made in the past 20 years; locking it tells me you've loaded it down with so much unnecessary crap that it's not worth touching with a ten foot pole.
A service that chooses pocket-sized screens as the class of device to lock it to is worthless. There's a reason books aren't printed on index cards, and it's because you're supposed to be able to actually read them. With your eyes, not a microscope.
And a service whose website pulls the "Are you sure you want to leave this page?" popup bullshit when you try to leave is out the fucking door faster than you can say "malware", holy shit.
I will not ever be reading the official English of this one.