TAS question - why does this HP model show up so often ?

[Gene]

On TAS (ok, EBAY), it seems to me that one SPICE series calculator shows up much more often that any other spice, perhaps more often than all other spice models combined.

It is the HP 38E/C.

Granted, you see the HP 31E, 32E, 33E/33C, and 34C on ebay. You also sometimes see the HP 37E (although IMO this is pretty rare), but check me out if you wish, but it seems the 38E/C shows up MUCH more often.

My question is: Why do you think that is ? I have some thoughts, but I'd like to see if anyone here has an opinion.