It depends upon what you're trying to achieve.

To run software, emulation is great. To develop software, emulation is great. Anything that deals directly with hardware, well, emulation isn't going to cut it.

Then there are the other reasons, ones that have nothing to do with the hardware itself. Personally, I use vintage computers as an escape from modern computers and as a reminder of what the technology could have been. I'm not talking about it being slow, unreliable, or downright difficult to manage. I'm thinking more along the lines of being simple enough to understand and a lot more personal. A lot of what we call progress is a mixed bag. Yes, the performance of modern computers is amazing and it comes at the cost of complexity. On the other hand, we have a lot of complexity that is not necessary for day to day use. Yes, having access to a literal world of information at our fingertips is amazing. On the other hand, our computers are also at the whim of the outside world. In other words, there are a lot of tradeoffs.

For some things, emulation is the perfect solution. For other things, it simply won't work.