i used to travel with (2) laptops on business trips - a work one and a person one . when i got an iPad, i ditched the personal laptop and just travel with that and my work laptop. i missed having the physical keyboard and cursor input so i bought a Kensington case + BT keyboard and then a BT mouse (jailbroke my iPad 3). now i have laptop functionality with the benefits of the iPad (iOS, long battery life, light weight, etc).
just as i used to think an iPad/tablet was useless, i couldn't believe i was without one for so long. just as i used to think a keyboard+mouse was useless with the iPad, i couldn't believe i was without them for so long
it all comes down to personal preference. we can't judge how others prefer to use their tablets. after all, it is their device and they can use it however it suits them.