Is UPS necessary to have for a PC?

It depends on your situation. There are those who will disagree, but I believe that in most of what we call the "first world", the power grid is reliable enough that a UPS doesn't provide much additional protection beyond what a good surge protector will give you. A rare power failure isn't going to damage most things.

Where a UPS really shines is in situations where you have a lots of small brownouts — the power doesn't cut out entirely, but it wasn't all there for a brief moment either, and this happens frequently (numerous times per day). This can happen in places where the power is less reliable. For example, you may be in an older building, a very rural location, or in a country where the power situation is less stable. In that case, a UPS will definitely pay for itself quickly, and you want to get one that not only provides stand-by protection but also what they call "sine wave output".

And, of course, you might also be going for a high-availability solution. In that case, a large UPS (and maybe even generators) is a must.

Looking at your location .. In India, the quality of power is not good (there are power fluctuations) and not to mention that we dont have continuous power supply 24X7, UPS helps in providing the backup power required to clean shutdown your system and save your work in case mains is down. Invest in a good UPS which also provides Surge protection /Voltage stabilizing