Okay, I have to really jump in here and agree with the lack of motivation and/or readiness! Remember, this lack of motivation and feeling like (hey this is too hard, I can't learn this, etc...) You know, the 'turn-off' factor. Well, these things do not, in any way, mean that your kid is not 'smart' or is not 'ready'!!!!
With DS (just turned 5) He also is very UNmotivated when it comes to the alphabet, etc... He is all boy, wants be active and interested in trucks, tractors etc... Well... We did overcome this - (He is experienceing the same block now with numbers though....) Here is how it worked for us.
I did have to make it a game. I had to focus on just a couple of letters that I KNEW that DS could easily indentify, without it being 'hard' or 'learning'.
The letter S is easily recognizable. One of the letters that is simple curves, easily recognizable and not easily confused with any other letters at all, and also, looks the exact same in upper and lower case. The letter S could also be easily be assocated with the shape of a Snake. Like with a little cute snake head on the top end.... So, we had fun making up little cute toddler stories like: The slithery snake sat in his seat and sipped his soda thru a silly straw.... That was the breakthrough!!!!! There were also stories like: The Big Brown Bear Baked some Bread and ate it with Butter.... Fun, cute, and it worked!
Then, once it all clicked with DS that yes, he did know letters, and could learn them... We make up a game. Using index cards and envelopes, I make the envelope to be the mail-box, like with a big 'S' depicted as a snake, and then matching cards, which are, happy coincidence, the 'letters' that go in the mail boxes.... He LOVED delivering all the Letters to the right characters.... ( Snake, Bear, etc.....) Bing Bang Boom, DS was learning the Alphabet!!!!
Hope this helps, and Good luck!!!