A large reason was because the English (later the British) started the colonies with the intent of staying there permanently. As a result, men, women, and children were all sent to the thirteen colonies and population was able to grow exponentially. People went for various reasons, ranging from religious freedom (like the Puritans who tended to settle in the north east) or perhaps second or third sons, who, if they remained in Europe, would not inherit their father's lands; often times they went to the New World to seek their own fortune.

In New France, the "colonists" tended to be fewer in number largely because breeding and colonising was not really a goal for them. In Canada in particular, many men went to trap furs to sell back to Europe, and to trade with the Indians. Very few women came to the New World from France, and although some Frenchmen took Indian wives, no population boom really occurred. Additionally, I recall reading that the French prevented Huguenots (protestants) from leaving to the New World, even though they were probably the ones who would most want to go (to avoid persecution).

Basically, it was different focuses and different goals at the time. Compared to the English, the French had little interest in growing their colonies until it was really too late, much like how England did not start to begin colonising until the 1600s.

American Pageant (AP US History textbook) does a good job summarising much of the early north american colonial history.