3G & 4G Tablets...Do we really need them?

In times when we have smartphones that can all be used as hotspots why do we need 3G & 4G tablets? I was in a hotel in London the other weekend and was pretty annoyed when the wifi just would not work, but then I remembered I had internet sharing on my 920 and because I was in London could use 4G rather than 3G that I get back at home, before you know it I was on my Surface browsing the net on a device that doesn't have 3/4G. Worked just perfectly. Devices are normally around 20% more expensive over their wifi counterparts and then that added monthly cost of a plan for the device on top. Much more expensive that just adding some extra allowance onto your phone plan. What do you guys think? do we need them or are they just making us spend more money on the device itself and then even more on monthly plans that we simply don't need (in my view of course).