I'm not sure what that has to do with it. Even if you are ok with the idea that integers and "decimal numbers" are different, it's still confusing that 0.1 + 0.2 != 0.3.

It's confusing because it is very difficult to look at a decimal number and know whether it can be represented exactly as base-2 floating point. It's especially confusing because you get no feedback about it! Here is a Ruby session:

    irb(main):001:0> 0.1
    => 0.1
    irb(main):002:0> 0.2
    => 0.2
    irb(main):003:0> 0.3
    => 0.3
    irb(main):004:0> 0.4
    => 0.4
    irb(main):005:0> 0.5
    => 0.5

They all look exact, right? Well actually only 0.5 is (IIRC?). All the others are actually approximations internally.