Why do guys lose interest after "the chase" is over and he gets what he wants? Why?

I feel like a lot of my interactions with guys end the same way...

(obviously not an actual conversation but actions and implications)

Me: "ya this is cool. i really enjoy spending time with you. lets see where this goes"

Him: "Omg yes! You are awesome! I want to spend all of my time with you and include you in my life and be there for you"

Me: "Oh really? Thats great! Ok lets spend all of our time together!"

Him: "Actually... Nevermind. Im probably not going to call you again. Ok bye"

What is up with that?
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"Ghosting Out" - My new most hated phrase in the English language...

www.thedatereport.com/.../
Why do guys lose interest after "the chase" is over and he gets what he wants? Why?
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