HunterK said: "She is the only cast member that is a household name, or at lest tot he crows they are going after. Why wouldn't you use her name in advertising? The show isn't about teenagers, yet marketing is sending out a promo for them."
If they can fit her into the advertising seamlessly, it probably wouldn't hurt but it's been 25 years since her last big TV series and 16 years since her last time on Broadway. I can't imagine many people going to see this just cause of her. She's a name people will know but in 2018 clearly more of the "Oh look honey, Marilu Henner is in this, too" rather than "Honey, Marilu Henner's back on Broadway. WE GOTTA GO." I think you're kidding yourself if you think otherwise. Also, the promo they sent out may have had a discount for teenagers but it was targeted TO their parents, the ones making the decision about whether to buy tickets. They're basically saying to their target market "you know you'll enjoy it but we think your kids will too so here's a cheap ticket so you can bring them." I can't fault them for knowing who their target market is and going with a unified "band focused" message.