Why does Bootstrap float their span12 class

Question

Was answering another question about centering a div that had the bootstrap's span12 class applied to it, and part of the solution was to reset the float as the span12, as well as the other span* classes, are floated.

Since span12 width is 100% when combined with row-fluid and 1170px when not (and other sizes that I suspect are meant to fill most of the area on different screen sizes)

This to me suggests that it is mostly a standalone grid item: not meant to have other grid elements floating along side it.

I could see if they wanted to allow for having other grid elements along side it for really huge sites (screen widths of like 2560px etc), except this would not work at all when using row-fluid as the first one in the row would take up all the space as it uses 100% width.

But I personally have not seen many, if any, sites that would use such a huge width that would allow for using a span12 grid element along side other grid elements.

So does bootstrap implement other styling methods that make it necessary to float the span12 class? Or are they just anticipating future use for huge sites?

As I use bootstrap myself, if it is necessary for other styling techniques I do not want to end up one day having removed the float when it is needed and also do not want to mislead others when answering questions if the resetting the float would end up messing up their layout when using bootstrap.

Edit

As DontFeedTheCode points out this has been addressed in Bootstrap 3, all the other grid classes get floated while the 12th one does not.

in the 2.3.2 version looks like they were using [class*="span"] as the selector for setting styles so span12 gets selected by accident

Answer 1

As bootstrap is written in LESS, and in 2.3.2 all span classes were generated using .gridColumn() mixin - all span classes had the float:left;. This is not for any large layout like 2500 or such.