There are several reasons why you might consider a firm mattress:

Better Support: 

Comfort: Plush mattresses are designed to provide a soft, cushioned surface for sleep, which can be particularly beneficial for those who sleep on their side or those who prefer a more gentle sleeping experience. The plush surface can help alleviate pressure points and provide a more comfortable sleeping experience.

Support: Despite their softness, plush mattresses can still offer good support for your body. Many plush mattresses are made with materials that conform to the shape of your body, providing support where you need it most.

Pain relief: Plush mattresses can be particularly beneficial for people who suffer from joint pain or other conditions that make sleeping on a firmer surface uncomfortable. The softness of a plush mattress can help alleviate pain and provide a more restful sleep.

Motion isolation: Plush mattresses can be an excellent choice for couples because they often have better motion isolation than firmer mattresses. This means that movement on one side of the bed is less likely to be felt by the other person, which can result in a more peaceful sleep.

Overall, a plush mattress can be a good choice for those who prioritize comfort, support, and pain relief in their sleep. However, it's important to remember that everyone's preferences and needs are different, so it's important to try out different types of mattresses before making a purchase to find the one that works best for you.