That's a perfectly acceptable personal decision, but bad advice to give to others. I'm also fit and healthy (5 a day everyday, exercise every day, compete in triathlons) and my last brush with flu (confirmed at the Dr), in my late 40s, put me in bed for 3 days, and seriously fatigued for several weeks afterward. I had to postpone a holiday for a couple of months. If the flu shot can reduce my odds of a repeat I'll take it.
I also know some very healthy adults (also runners / triathlete) who've been poleaxed by Covid. Not hospitalized, but not fun either. Again, one booster a year seems like a reasonable precaution.