1/ GW1 pve relies heavily on wiki if you want to do it efficiently. For second or third playthroughs such as hard mode, a wiki is really useful. Same for skill caps, exploring, WiK.... As for pvp, it used to be really useful to check a guilds ranking during warmup in Tombs. A second screen is bliss in this game.
2/ Increasing efficiency is not just for work, anyone making youtube movies, reason music, websites or just anything will need a second screen to get anything done, especially while doing tutorials. It is possible without, but so is doing tour de france without a bike.
3/ If you have a company laptop, a second monitor is a very small investment for added fun in Guild Wars.
4/ If you have any form of responsibility in your job, working from home is inevitable, which almost forces you to buy a second monitor which, luckily, is tax deductible.
Basically the conclusion being, second screens are cheap, spares are freely available on the market, and anyone with a second screen won't give it up anymore. The percentage of people with second screens is rising very steadily because of all those factors. Those are clear facts, which allows me to state that I expect most people to either have a second screen or be able to get one if they want to, especially if they have a notebook. Accordingly I can make the joke to play GW1 and GW2 at the same time since 100% of the gamers have the option to play dual screen for minimal investment if they want to. What you think is irrelevant in the face of facts.