Yes, muscle strength training fitness programs necessary for everyone. They help you to rebuild muscle as you get older because during this time your body will become weaker. It is great for pregnant women during labor when you have to lift and push it prepares you to fight through the pain.
People are quite varied in terms of musculature. Some have minimal muscle mass and others who have never trained have prodigious muscle mass. Some could certainly benefit from such training, but its certainly not needed for everyone. People are different in about every way that a person can be different.
Not everyone needs to build muscle. It does help in many individuals, but some cannot perform the excesses safely enough to practice strength training. The elderly lose a lot of their mobility as they age, and trainers who push them to full-range strength training are asking for injuries. Many younger people have the same issues and can get injured doing exercises incorrectly. These injuries can stick with them for years or indefinitely.
I do not believe muscle strength training fitness programs are necessary for everyone. Some people do not want to bulk up or gain a lot of muscle, they would rather be lean. There are many different types and styles of exercises and it is certain that everyone needs a little bit of exercise, but they shouldn't feel the need to conform. They should choose what works best for their goals.