Actually, some protestant churches also do not immerse (the Methodists and the Episcopal churches come to mind).
Um, no it doesn’t…
Immersion is (and has always been) the preferred method of Baptism, but the Church has always recognized that full immersion was not necessary. As churches were built away from rivers or lakes (in times and places where indoor plumbing was not available, and chlorination was unknown), it became more difficult to maintain a baptisimal pool, so many such churches (as a practical matter) adopted non-immersive Baptism. Gradually, this method (valid, but not preferred) became the norm.
However, in recent years, the Church has emphasized a return to the practice of immersive Baptism. In any church of modern construction built in a society where it is not impractical to maintain a Baptisimal pool, you will always find such a pool, and it will be used in Baptism.