FL Studio has to sell free upgrades, because that’s how they can stand out in a crowded market. Being a little facetious: They can do this, because they sell at a low price, so there’s tons of wannabe bedroom producers who buy it, try it, and then move on, so there’s a reasonable revenue stream of 16-year-olds with their first convenience store paycheck to spend. (A new batch every year!) (Some of my favorite EDM artists use FL studio, so, this is just an illustration of a business model!)
Cubase does not use that business model. Cubase is an ecosystem, largely for people who do integrated media and music production, plus a number of other use cases. The market of Cubase users does not get a new batch of high schoolers to sell to every year, so they need a different model to keep the product alive and moving with the times. That model is a higher initial selling price (for the Pro version,) and a somewhat-regular upgrade price.
If you rely on Cubase, and get value out of it, and want it to keep thriving as a production software suite, then you should keep paying them money. If you’re OK with FL Studio, and don’t need Cubase, then you should not pay Steinberg money for Cubase. That’s how business works! Asking for things for free might be nice wishful thinking, but remember the saying: “whenever you’re not paying for the product, you ARE the product!”