One thing I've found in fitness is that people need to do what will keep them active and for many, that requires specific guidance or goals. General prescriptions like "use your muscles by being active" is fine, but what does active mean? Some people like bodybuilding, or powerlifting, or powerbuilding, or crossfit, or hiking, or basketball or whatever and if those things get them active, then that's good.
The current physical activity guidelines call for 150 minutes of moderate intensity cardiovascular training per week and at resistance training on at least 2 days per week. There's lots of ways to get there, and maybe strength training is the way to do it for some people. Even if that's not the focus, however, people should set aside some time to focus on resistance training because it provides a number of long term benefits.
You don't need to grow anything. Use your muscles by being active, a hard thing to do in IT.