Tom Holland and Zendaya's PR strategy is leaving millions on the table. Pros say that's a good thing.

Tom Holland and Zendaya promoting "Spider-Man: Brand New Day" in Germany. Tristar Media/WireImage Tom Holland and Zendaya recently married after years of keeping their relationship low-key. Outside of promo tours for "Spider-Man," the couple rarely appears in public together. PR pros say discretion benefits the couple's image, even if it's not the most lucrative strategy. If you look closely at a patch of skin on Zendaya's ribcage, you'll spy a tiny, discreet "T" tattooed in black ink. Her…