Only if you churn -- signing up for a card, redeeming the signup bonus, then signing up for another, and so on.
And card issuers know about churning. The highest-value cards also have limits to how often you can churn. Chase's "5/24" rule (if you've opened 5 or more new credit cards in the past 24 months, anywhere, Chase will automatically decline you on any application for one of their cards) is one of the more well-known anti-churning tactics, but not the only one. You have to immerse yourself in the churning/manufactured spending world to really get much more than one or two free tickets from card signup bonuses.
On the other hand, if you already travel enough to reach at least mid-tier status with one airline, it's often worth it to do so; that's when you start getting into large RDM bonus territory. Combine with the airline's branded card and you can easily generate enough mileage to take a nice vacation every year.
And card issuers know about churning. The highest-value cards also have limits to how often you can churn. Chase's "5/24" rule (if you've opened 5 or more new credit cards in the past 24 months, anywhere, Chase will automatically decline you on any application for one of their cards) is one of the more well-known anti-churning tactics, but not the only one. You have to immerse yourself in the churning/manufactured spending world to really get much more than one or two free tickets from card signup bonuses.
On the other hand, if you already travel enough to reach at least mid-tier status with one airline, it's often worth it to do so; that's when you start getting into large RDM bonus territory. Combine with the airline's branded card and you can easily generate enough mileage to take a nice vacation every year.