Speaking only for myself:
- It keeps our options open for camp / classes. Being able to say, "you already qualify for this" rather than, "you could take a test to see if you'd qualify for this" makes a big difference for an 8yo.

- It's a cheap way of doing achievement testing beyond the low-ceiling stuff the school does.

- It's a cheap way of exposing her to material she may never have seen before. (I was a psych major in college, and had never heard of I/O psych before it came up on the GRE - if I had, that probably would have been the direction I'd have gone.)

- My kid is agreeable enough, so I assume that she likes it at least somewhat. If she'd come out of the SCAT (a very short test) as a frazzled ball of tears, I wouldn't have signed her up for EXPLORE (a very long test).