Our parents and/or grandparents didn't go to the gym so why do we need to exercise?
Life has changed so much in the last 100 years and with so many time saving devices, even a remote control for the TV and a phone in your pocket mean that we are all much less phyically active than previous generations.
So the answer is..... probably. Unless you can be physically active every day including, digging the garden (instead of lifting weights), walking to work and then not sitting for more than 8 hours a day .... and so on.
It's also worth being aware that you can't out train an inactive lifestyle, so working out for an hour each evening after sitting in a car/bus on the way to and from work, sitting all day for work and then after the gym sitting in front of the telly or your computer and you could be storing up issues for the future!