It seems to me that Giant spends a lot less money on marketing than Specialized, Trek, Cannondale, Bianchi, etc. This keeps their cost down. I very rarely see advertisements for Giant. I remember back when watching the Tour de France it seemed like it was the Tour de Trek. Now, on the 'net I regularly see ads for Canyon, probably because I've watched GCN a few times. Advertising and other marketing is very expensive. The bike reviews in magazines and on many websites are often payed promotions. I don't see a lot of reviews for Giant products.
Consider that in January of 2019 Specialized spent over $700K to secure the Roubaix trademark rights from Advanced Sports Enterprises. Prior to this Specialized used the trademark under license, probably paying some amount for each Roubaix sold. This expense was a business decision and likely deemed to be in Specialized's best interests. If the $700K trademark expense was amortized at $10 per bike, this would take 70,000 bikes to recoup. Profitability is important in business. In order to be profitable these expenses are passed on to customers as higher sales prices. Specialized then has to market their bikes in order to create the impression that their Roubaix is worth more than a comparable Giant.
It's about building product 'status' through marketing, and the charging the customer for the marketing.
Is a Pinarello Dogma Mucho Fantastico really better than a Giant TCR with the same components? Some washed up ex-racer may write a magazine review and state that it's more "responsive," "stiffer," "provides better road feel," or something. But he will have been paid to write that statement. Note that such statements are subjective and that real data; transient response time, stiffness measurements, vibration data, etc. are never presented.
Giant has reason to limit marketing their own products. Since they manufacture the many of their "competitors" bikes they could hurt themselves. Giant is in an unusual position whereby it appears to compete against itself. Giant, like many businesses, probably has employees whose job is to understand the bicycle market and develop a strategy that maximizes their profits.