Why use a deep spool reel for cranking?

[The Rooster]

I'm curious.....if I can only make a certain distance cast that any normal baitcast reel with a 12lb/120 yd spool holds plenty of line for, then why do I need a deep spool reel for cranking? I don't understand the need for all that extra line. I do realize large deep diving cranks may increase cast length and if that's what is behind it then why not have deep spools for slow rolling large spinnerbaits, too?  My large spinnerbaits really strip a reel of line.

[cortman]

I think you answered the question- you need to get deep diving crankbaits out further, since it takes a bit of cranking to get it down to the maximum depth. More distance = more time at max depth. With spinnerbaits that sink you can always just pause the retrieve and let it sink. Can't do that with a floating crankbait.

[LgMouthGambler]

Think about if someone uses 20# mono. The thicker line allows for less yds per spool. Deep enough spool to cover a variety of uses.

[njpaulc]

The more line you cast off the reel the smaller the spool diameter.  The smaller the spool diameter the less line is retrieved per handle turn.  The deeper and wider the spool, the more consistent the retrieve rate .

[Lee Smith]

The more line you cast off the reel the smaller the spool diameter.  The smaller the spool diameter the less line is retrieved per handle turn.  The deeper and wider the spool, the more consistent the retrieve rate .

Zactly! 

[The Rooster]

Several great answers.  Thanks to you all.