$usercache variable and getuserinfo() function

[Tae-Hwan]

alright, my index.php is calling this query:

Query: SELECT user.*,userfield.* FROM user LEFT JOIN userfield ON userfield.userid=user.userid WHERE user.userid='1'
Time before: 0.030212998390198
Time after:  0.031402945518494

i did a little investigation, and found that it's coming from the function, getuserinfo(), which is located within admin/functions.php. the weird thing is, this function isn't called in index.php, forumdisplay.php, or showthread.php. it's called in member.php, and there's another function in functions.php that uses the $usercache variable to get the permissions of the usergroupid. my question is simply, why is it necessary to call and join the entire row of the user and userfield tables on every pageload? for the purposes of getting permissions, i kinda understand the user table, but why the userfield table? this is mostly for curiosity's sake, btw..