No not at all, activity monitors can be great for a few reasons:
First of all, 10,000 steps roughly works out at about 5 miles. Now you roughly burn 100 calories per mile you walk, so if you hit your 10,000 steps per day, it could equate to burning around 500kcals (depending on your size and weight etc...). Beyond this, getting up and walking is going to have a positive impact on your cardiovascular health, posture and joint health and if you're getting out for a walk, stress and mental health.
Beyond this, having a target to aim for can promote some really good behaviours. Having that app on your phone with a 10,000 step target (or whatever you've set yours at), helps you to build the habit of being up, active and walking around on a daily basis, because come the end of the day, you want to see if you've beaten your target.
That competition is a good thing as well and by getting friends involved, seeing who can get the most steps in per day can help to hold you all accountable, help you all to become fitter and healthier and you can have some friendly banter while doing it.
Finally, walking that bit more every day might not sound a lot, but it works on the principle of marginal gains. By doing that extra 1% here, then add that to another 1% you might get from adding an extra handful of veggies to your meals, added to the extra 1% from making 10 minutes per day to stretch, then these all start to add up and without feeling like you're made any drastic overhaul to your daily schedule, you've already made some pretty positive changes and should see some good benefits to your health.