I nearly always plan routes on my phone. After all, it's the device I use for navigation attached to the stem of my bike.
> Why in the hell wouldn't you prefer to use a nice monitor with a mouse for a complex task like this?
The task isn't very complex with a decent UI. See for example the open-source app OSMAnd (Android & iPhone). Also, I am rarely at my desk, but I always have my phone on me. There can also be the issue of "Neat, I made a route on a big screen; now, how do I get it on my phone for real-time navigation?" depending on the app you are using.
Thia isn't to say you're wrong. I much prefer my monitor and mouse for anything of reasonable complexity. But I increasingly find myself in the minority in that regard among people I know. Hell, I even find myself in the minority for using a laptop for tasks sometimes.
I couldn't imagine trying to build a complex route on a tiny screen with a crappy phone UI. I am starting to feel like an old man yelling at clouds here. Why in the hell wouldn't you prefer to use a nice monitor with a mouse for a complex task like this?