Why would a second MRI be requested? ?

It's likely that your doctor ordered an MRI with contrast to be performed and they forgot to give you the proper. Amount of drink in order to accomplish that MRI they're supposed to give you three bottles of shading material.

So they're going to do the MRI over the way they're supposed to

What part of .........."with contrast"..........do you not understand?

The doctor who reviewed the first one may have seen something he or she was suspicious of. That's the usual reason why this type of thing gets repeated. Or perhaps the film wasn't of good quality the first time. I've had that happen- it's a nuisance, but it seldom means that anything is wrong.

It's also possible that somebody found something they didn't like, too, and they want to look at it from another angle, or with more light, or contrast, or whatever, to make sure that it's not something to worry about.

MRIs can be retaken with contrast, at a different angle or in more detail in an area of concern. Or to confirm that all's well,

If an abnormality is discovered with a non-contrast MRI, the procedure might be followed up with contrast to see more details.   A MRI without contrast is typically done first when screening for tumors or other soft tissue abnormalities that are not certain to exist.  Contrast dyes are moderately toxic and they can cause some serious side effects, so dyes are generally not used unless docs are fairly certain they need higher resolution to get the information they are seeking.

They just want more money! MRI machines don't actually do anything except make noise! Its all a scam! 

They do it if you have cancer in the brain

Not necessarily, it may be that the initial study didn't provide the level of detail necessary.  Or they screwed up and should have used contrast media in the first place.  I'd say don't sweat it, but I know how it is.  Best of luck to you that everything comes out normal.