It might be ideal for company's to allow its staff to use their personal computer at work, if they are have all lose ends tied up. At the end, I feel it's the companies role that whether or not they should do this. Let's answer the question why this happens? Why does someone want their personal laptop at their offices? The answer is pretty simple, they are comfortable with their own systems. Maybe they are developing such sort of work that require a given hardware, if that's not available at the company, people do turn to their own personal computers. It has happened with me as well. I use a Mac and design stuff and my office provided me with a Windows PC. And as I feel, Mac is better for my workflow as well has better web development tools than their Windows counterpart. And therefore I started using my Mac device at work for all my dev needs. This can happen with you as well and therefore you might think it's a good idea to use your own device at office. Therefore, ending it, I would say that companies should try and let people select their own hardware of choice rather than giving them a standard device.