The reason logic programming is not widespread is 2 fold:
1) It is a new paradigm (just like functional, object oriented) are new paradigms. That makes it much harder to learn. It is not like going from Java to C#.
Look at this http://dtai.cs.kuleuven.be/ppcbook there are solutions to problems in Prolog. Solutions are amazingly short, and concise. They are beautiful in how succinct they are. But few programmers could produce them. It is just too hard to make incremental updates and debug logic programming.
2) It is not really that useful in real world as a general purpose language. And it is sure not for the lack of trying. It was supposed to be the 5th generation language in Japan, the future, money and brainpower was thrown at it and ... not much happened. People wanted to server data over the networks, render games, search databases, sort data, multiply matrices and in not too many of those domain logic programming screams as "this is the most obvious paradigm". Because it isn't.