Using CALL SPRITE over 1000 times faster than FOR loops

a while ago I just thought 'huh, why is the raycaster calc84 so fast?' Since I am no computer science genius, I decided to test it using the scientific method, using code similiar to this:

DEF WP SP,X,Y,Z'weak perspective(basically perspective minus camera rotation)
 VAR X%,Y%
 IF Z == 0 THEN X% = 200:Y% = 120:SCL = 1 ELSE SCL = 1/Z
 X% = (X/Z) + 200
 Y% = 120 - (Y/Z)
 SPSCALE SP,SCL,SCL
 SPOFS SP,X%,Y%
END

DEF WP2
 VAR X%,Y%
 IF SPVAR(CALLIDX,2) == 0 THEN X% = 200:Y% = 120:SCL = 1 ELSE SCL = 1/Z
 X% = (SPVAR(CALLIDX,0)/SPVAR(CALLIDX,2)) + 200
 Y% = 120 - (SPVAR(CALLIDX,1)/SPVAR(CALLIDX,2))
 SPSCALE CALLIDX,SCL,SCL
 SPOFS CALLIDX,X%,Y%
END
'----initialize----
VAR X = RND(100),Y=RND(100),Z=RND(10)
FOR I = 0 TO 511
 SPSET I,0
 SPVAR I,0,X
 SPVAR I,1,Y
 SPVAR I,2,Z
 SPFUNC I,WP2
NEXT
'now the testing begins:
M% = MILLISEC
FOR I = 0 TO 511
 WP I,X,Y,Z
NEXT
FORTIME% = MILLISEC-M%
M% = MILLISEC
CALL SPRITE
CALLSPTIME% = MILLISEC - M%