With more reliability on having your computer "hold" all of your important documents, data, pictures, and videos; Solid State Drives are more of a demand in today's computers. But everything is going on the "cloud" now right so what is the big deal? Well, do you really trust having everything on your cloud/web based account? Personally, I still have vital information stored locally on my hard drive, but if you are a fan of the cloud setup, cloud services usually have a annual premium fee for keeping your files.

So why SSD [Solid State Drives], and why would I spend significantly more money for a lower amount of hard drive space compared to typical mechanical hard drives? I know, I know, it doesn't make sense to pay $200+ for 120GB SSD when you can buy 1TB 7200RPM at $80. It will make sense once you understand the technology behind it. SSD, no matter what type, or model will always do significantly better than any mechanical drive.
Any time you load a program, play a game, or move/import data you are accessing your hard drive. Your typical platter mechanical drives have a speed of 60-150MB/s depending what size the drive is [laptop size=2.5", desktop size=3.5"]. When the disk needs to read or write a certain track, there is a hesitation that happens. That doesn't sound to bad though, however, think about Windows and how many thousand blocks of data it needs to access and read. The file sizes for this data ends up only being in the megabytes, so you don't need anything huge to handle these reads and writes. So the more sensible question is: Why have a huge hard drive as a system drive?
SSD have no mechanical/moving parts, eliminating vibration and movement disk error factors. They are much more robust since they hold data on NAND flash memory chips. Because of the memory chips working together side by side, you can have access speeds from 200-500MB/s. SSD are 10-20 times faster than your typical hard drive. So if your concern is speed while running applications, and reliability on a drive, SSD is an excellent choice for a computer. If you need to store large quantities of data, a mechanical drive should be setup as a secondary drive within the machine. Even when doing that I would still have either a RAID setup or an external backup just in case that 7200RPM hard drive decides to just stop spinning.