What do you buy a bike for?

Got into a discussion tonight with a fellow cycling friend about what you buy a bike for. 

He and I are roughly in the same boat when it comes to trying to figure out what bike to buy and the lack of availability of a bike to test ride in Atlanta. 

So....

He was of the mind that you buy the bike more for the components rather than the frame. 

I was more of the mind that you buy the bike for the frame over the components as they are interchangeable. 

One caveats: If the bikes in question are of different frames Steel vs. AL. How do you apply the debate above? 

Frame and Fork is the heart and soul of a bike. Steel has a reputation for being more durable and more comfy to ride.  My next bike will be steel. Here is a pretty good primer on the subject. http://sheldonbrown.com/frame-materials.html

EagleGrinder wrote: what you buy a bike for. 

I buy bikes to exercise and socialize.  Mainly to exercise.  For the way that I exercise:

I would not own a road style bike with mechanical Shimano shifters - so my choices on a complete bike are severely limited. And I go for value across a given group set and spend money when I can notice a difference with respect to my abilities/application (so I have Red cranks vs Force on my road bike).  I'll admit that sometimes I go with what looks better - if there's no discernible difference in the operation (the Force brakes and RD looked better on my road bike than the functionally same Rivals).  My Shifters are Red - but I would have been just as happy with that year's Force.  Got an insane deal on the Red set. 

My cross bike is going to be Rival across the board with the exception of some Force chain rings (situational upgrade - not performance based as I have no experience with the Rival rings).  The only thing I am worried about needing to upgrade is the crank.  We will see. 

I would not mind owning a steel, al-alloy or ti-alloy bike (tried them all and suspect that my exercising would be essentially as efficient on any of them if they were well built and stiff where I need them to be) - but (at least mid-grade) carbon works best for me.  

For my wife - who only rides slowly for pleasure on greenways and some charity road rides - it matters little.  Al-alloy and sora are fine for her. If she got serious about using the bike in a more dedicated fashion - then it would make sense to be a little more analytical for her.    

My opinions are mostly based on trying stuff and figuring out what works for me.  Not to discount the process of reading the reviews and insights from industry experts - that stuff is helpful too.  Consensus opinions, on the other hand - mean less than nothing to me for the most part.