Actually while running during lunch I thought some more about this question and I'm going to correct myself. It does have SOMETHING to do with space. However, the jump from 44.1 to 48 kHz is minimal. The jump to say 96 KHz would eat into the space on the tape. However, when compared to jumping from 16-bits to 24-bits, the jump isn't as bad. Which is another reason a few of the DSP engineers I knew always told folks to use 44 or 48 KHz and 24-bits over using 96 KHz and 16-bits when space was an issue. Actually Emagic at one time had some info where they told folks in vivid details why they generally stayed away from 96 KHz.
Wayne