Crystal SMD housings is offered in a range of sizes, in many cases quite similar dimensions.
Is there any reason why some prefer the housing and ignore the other?
My actual choise is case 5x3.2mm any as this
You'll notice a relation to frequency, low frequency crystals have a certain minimal resonator and thus case size. Limits are however continuously changing. The other point is design form factor. People are working in quite different dimensions, so there can't be a "fits all" crystal size.