- They are not your exact desired specs- they're not bespokely made.
No drilling holes Quick to assemble Quick to change components arround you need all the components to make circuit more expensive than PCB and Breadboard
Advantages are that you will get faster, more up to date equipment. Disadvantages are that you will have to spend money, products are almost old when you buy them, plus you will need to make sure there are no compatibility problems.
It makes them cheaper to build. Therefore they can sell them at a competitive price.
Cost, cost and cost.When you design a computer it is all about performance, and to sell it, the price need to be competive. If it is better than competitive, and you can make a device with more bells and whistles, better performance, better battery life, bigger disks and still to a lower price, the difference is the profit you can make. Since standard components are produced in large numbers, these are cheaper than those you design yourself, and make just those few you need. So standard components are preferred, until you elect to make something your competitive edge. This you spend your effort at making better and leave all the other things to standards.
Changeman is a version and configuration control software for Mainframe which gives you (the standard) facilities like bundling the related components (programs JCLs etc) of a release together version control for installation / rollback of components storage of compiled listing and also provides the interfaces (screens) for compilation analyzing the relation between components etc.