... I mean not to me! But it happens. :p  
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Ok, it does happen to me, occasionally. When it has I have asked what's up and heard the "I'm just not into it" response every time, despite feedback from other SB's that I knock it out of the park for them.  This leads me to two possible conclusions:  
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1. She's really not into it, or
2. I'm just not doing it well  - for her. And presumably she's not comfortbale telling me that or she's not good at  providing feedback about what gets her off.  
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There's a third path around, let's call it "freshness".  Once in a while, I have found myself in front of a slightly "wilted" flower. It smells a little sour, it looks like it needs a little water, maybe some time in fresh air, ya know?  At this point, we each must make a judgement call:  go forward or retreat.  If you go forward, you may not be delivering your best effort, 'cause, you know, skanky pussy.  
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This happened to me on the 2nd BCD round with a new SB I added last month.  She took a 40-minute Uber ride to my place right after work. That meant she had not showered for at least 9 hours when she got to me and she, frankly smelled like shit. She was super horny and anxious to get me down there, as our 1st session started with abut 45 minutes of sublime scuba diving by me. She actually soaked my bed sheets so much I had to grab 3 towels and put them on the bed.  But this time, as I started to head south I was assailed by her full-day battle reek. So I just grabbed her hand and said "Hey, I need a shower. Come with me and we'll have fun getting soapy."  Of course I had just showered 15 minutes before she arrived. But it worked out.  

and Im very upfront that it is required and it is a deal breaker.

I’ve had one like that. She really wasn’t into it, but was a good fuck. It ended up as a deal killer for me. I love DATY as much as fucking.

Some women ruin their clit sensitivity by overusing a vibrator... If they are destroying themselves with a Hitachi that could be a cause...

I used to see this pro who just did not enjoy getting daty.  She let me do it some since I enjoy it, but really, it did nothing for her.  But she loved anal!  So much that one time she actually had a hands free O just from getting fucked in the butt.  So, who the fuck knows?

One goes so far as to say she hates the idea of someone's tongue on her anywhere.   She must have been tongue lashed as a child, I guess.

 
I enjoy doing it, but it's not a deal breaker.

The harsh reality is that they prefer the dick. Every woman I’ve banged multiple times whispers to me on the 2nd or 3rd time that they really don’t like oral and they just want my dick. The only women I’ve heard talk about loving oral are housewives whose husbands obviously can’t fuck because they’re too fat. This is during parties where the wives are all drunk and start to compare notes.  

Now I don’t think my oral skills are bad. I can consistently get them to come and squirt. I also don’t think my dick is anything special given it’s average size and shape. All I know is, I can hit the same spots with either my mouth and finger, or with my dick and I can give her the same kinds of orgasms but I can do it better with my dick.  I can give her about 1 orgasm with my mouth before my tongue gets a little tired, while I can go a ridiculously long time with my dick and they can come as many times as they can handle it.  

It’s also easier to be truly connected with her when your faces are near each other and your hands are free. You can touch almost any part of her body while fucking her.  You can also talk dirty, nibble her neck and whisper in her ears. Your tool chest is more limited with oral.  

I think it’s just really hard to have your tongue and fingers beat out an organ that was designed to pleasure a woman.  None of my regulars ever ask me for oral.  They only accept it for a change of pace or when they’re especially insatiable and I haven’t recovered yet.

I’m here partially because there is no Daty at home. Wife doesn’t like it.  I live the taste of a fresh flower, but I will do the shower trick when it’s a smelly snapper.  Wife is gone this weekend and I have some new POT SBs to try.  

Yes, I am odd, willing to do, but oral either way does nothing for me.   I tell an escort etc that up front (prefer to skip the oral stuff and give her some Esalen type message which really sets the mode (I've taught it for couples).  

Many times, when I suggest skipping the oral part, the gal will say something like "oh good, I'm not into oral either"    

I am not opposed to it but just will lose erection or if giving need a snorkel.   Would be happy to learn giving skills but just never had the right partner to train me and it would only be for her enjoyment since does nothing for me.  

Interesting is gals that it seems the only way they know how to put a condom on me is having in their mouth and doing oral to put the condom on - nice skill although not my thing