It's true that fractions can be replaced by simple decimals in some instances, but students need to be introduced to the idea, so that when they come up with fractions in terms of variables x, y, z, etc. they understand it. These would be essential to learn Calculus, especially from first principles. Even then, fractions shouldn't be postponed just because they're confusing and turn people off further study, they're not that complicated and don't require any memorisation. Postponing fractions in mathematical education would be like getting a football team to train without the ball until match day, IMO.