What is the reason behind this

Not necessarily true. Steel can attract magnets, that is why it is called a ferrous metal, meaning iron may be incorporated into steel to give it certain properties when needed.

Metals that do attract magnets are nickel and cobalt.

Some steels do not attract magnets - such as some stainless steels that have 10% or more nickel.

Good answers, steel is an alloy of other materials like carbon, nickel and iron.

urgetech: two things. First, did you notice that you responded to a post that is over a year old? And second - steel is not aluminum!