Dear website designers,
these days is quite common to have a computer monitor with Full HD (1920 px) or more width. And with the Windows key shortcuts Win+Left and Win+Right it's really comfortable to put the browser window in just half of the screen. By the way, don't you often do this when developing websites? I personally use it a lot. I use lot of web applications and the ability to have them side-by-side is often useful. Or having browser window in one half and some IDE or desktop Word or Excel in the other is also very nice thing to do.
The point I'm trying to make that having browser window 1920 ÷ 2 = 960 pixels wide on the standard desktop computer is something completely normal. And you really don't want to see the „tablet“ version, e.g. hide menus and stuff like that. By the way, do you really need to hide menu on a tablet with such screen width? I really believe, that this is doing „responsive web design“ without thinking. They may be good things to do when displaying page in such width, e.g. galleries can have two thumbnails per row instead of three in full width and so on. So yes, do responsive sites. BTW Bootstrap 3 has one breaking point with default width of 970 px so you can take that for distinguishing between full and half width.
But, for all good reasons, don't think that browser with width of 960 px is tablet. And even if it is, that you have to hide half of your controls! That's not responsivity, that's plain idiocy :-)
Take that as a New Year's resolution :-)