Why are companies bigger, than they are supposed to be?

When you look at the average IT company, you see the front-end (the product it offers) and that's all. Many people wonder why the amount of personnel is so large, for the seemingly simple product? Well, there are several main reasons, which I list below. 

1. Customer service and sales
2. Scalable Backend development
3. Research and optimization
4. Permanent security evaluation
5. Integration with others

1. Customer service and sales. This is the department (in IT companies it's often the same personnel for both tasks) that communicates with customers, prospects, and partners. It can be infinitely large, especially for a mass market product.

2. Scalable Backend development. Most (if not all) IT products (software) have a part, called back-end, which contains most of the business logic. For mass market products, this part must not just work properly, but also be scalable, i.e. be able to handle many requests concurrently. To do so, the backend runs on several computer systems simultaneously, and they must play nice with each other. such scheme of operations is called "distributed system". Design and maintenance of distributed systems are one of the most complicated tasks in IT industry, and there's always room for improvement in any distributed system.

3. Research and optimization. The efficiently designed and implemented system can perform much better, than humans, and human labor is nowadays much more expensive than computer systems. Thus it makes sense to put the most of the burden on computers. But their resources also have certain limits, and the more operations you can "fit" into a single system, the more commercially efficient and profitable (let's hope so :) your system is.

4. Permanent security evaluation. New ways to penetrate protection of computer systems are found and presented literally every day. This can lead to money loss or even more serious, even deadly threats. Obviously, this is not what any business would like to experience, so security evaluation, patching, further evaluation is the never-ending loop of work of IT security specialists.

5. Integration with others. IT systems rarely work in the isolated environment. Even when the software application works on the local computer, it is run on top of the operating system layer, and playing nice with the OS is a kind of integration as well. Now, the data must enter and leave the software system. Making this possible requires following certain standards, data exchange formats etc. All of this is also integration. Finally, the software rarely delivers the complete solution to some business problem. More often, the software is the part of the larger workflow and integrating into as many workflows as possible is important to deliver the better experience to customers and to grow the user base.