Menus and other non-gameplay related UI are actually much easier to create when they are driven by the same visualization code used in your gameplay. In the same way you display animate your game objects, you should be able animate your UI buttons and menus as well.
Think of a menu button as a game object with a different sprite. When polishing your game you'll be happy to have the ability to easily tween, scale and fade in/out your UI elements.
Since you don't mention a framework (such as ImpactJS or Crafty, for example) I'm assuming that you've got something home grown. If that's the case you may not have such generic ways to visualize game elements. While you can brute force through creating menus and title screens which do not share the same visualization code as your core game, you'll end up with something much less maintainable and extensible.
Because you're using HTML5 it's also an option to create your menu code using HTML DOM and CSS. While much of the animating and layout of menus will be easy with some CSS transitions, it's still (in my opinion) an inferior option to having your canvas framework be generic and flexible enough to easily create and animate any kind of game object.