Software Engineering is very different from other branches of Engineering in many aspects as a discipline. Making software is human and logic intensive.

It does not involve procurement of raw materials and their processing. It does not need high voltage like in heavy engineering.

It does not incur distribution cost of finished goods like cars or microwaves etc. Most of the software is distributed through network to the end user devices. Many ready to install software products like MS Windows, Oracle Database etc are distributed through DVDs or CDs. Their distribution incurs minimal costs in comparison with distribution of products like TV or refrigerator.

While a software engineer can think of working from home, it is not possible for a production engineer of a cement industry to do the same.

Open source software is made by a number of individuals distributed worldwide. In a similar way, a television or a car can’t be made by a set of people distributed worldwide.

I can’t imagine someone making and distributing cellular phones free. Where as, Open source software is given free for all.

Software can be repaired (bugs can be fixed) from a distance. The problem in software residing in a computer in America can be repaired from India. If the same problem is with the computer hardware, it can’t be repaired from India!

Additional features of a software can delivered free. For example, Adobe PDF Reader additional features can be downloaded from Internet and installed. Once we buy a bicycle or a car, we are not given any additional components for free by the dealer.