Let's talk about what are custom roms and so why should you install them in your android phone.Acustom ROM is a modified Android operating system that you can install onyour Android device that open-source developers have developed with a bunch of new features which you cannot see in normal stock rom like customization,battery saving ,stock android and many more.
Let's go ahead and talk about OTA updates OTA stands for over-the-air updates these are system updates provided by your manufacturers a carriers to update your phone to the latest system but some manufacturers stops updating on your Android operating system but bigger advantages of custom rom are it quicky gets OTA updates.
NO BLOATWARE and Adware
There are many stock rom like miui,color os which give bloatware and ads for revenue but in custom there is no bloatware or ads.It gives very clean experience to user.
Improved performance and better battery life
you can get better performance on your phone just like putting better parts on your car well you can do that most custom roms offer better performance no lag out of the box and also you can even overclock your phone to 19 gigahertz if you want custom roms also offer better battery life for your phone by better managing stuff on your phone such as multi tasking and gaming.
Perhaps well with custom roms you can change the whole look on your phone by installing a custom ROM that come with a bunch of themes you can change the theme also you can get roms like havoc os, aosp extended os etc.Some custom rom rom also give camera 2 api support which give full control on your android smart camera and advanced camera features.