If you happened to be in the incredibly fortunate position to have major label backing in the 70's - early 90s, then lucky you! Just book a studio in the sunny south of France, LA or the British Virgin Islands for 3-4 months, book your flight and worry about the music once you get there...
Sadly, 'for most' this isn't the case anymore, budgets and time restraints are tight, so the efficient use of studio time has become essential to delivering on budget.
So 'Pre Production' is more important than ever. If you're working with me or any Producer, it's a good idea to spend time with them refining the songs and arrangements, usually over a course of weeks before booking the studio. This will help the producer significantly in planning the recording session, i.e how long to allow for Drum tracking, what day should the session muso's come in? and even down to which studio will get booked, based on budget, technical and space requirements.
And Money... yes that chestnut.
Pre Production helps inform the budget and allow the Producer to plan accordingly, cutting the suit according to the cloth.