Building rides for real life theme parks isn't like RollerCoaster Tycoon in that it either builds and works or you get a red error dialog box. Every single major roller-coaster, including those that are replicated over and over again (like Boomerangs or SLC's) are still unique installations that are built to the theme park's unique set of requirements as well as local, state and federal engineering/safety standards.
If a theme park put a tender out for a roller-coaster, Gerstlauer aren't going to go "sorry, we have this model we'd love to sell you but like RollerCoaster Tycoon there's just not enough green squares" they're going to go "oh yeah, we can modify x, y & z to suit and it'll cost this." They're not like cars and they're not a smartphones - they're as customisable as houses.
Adding to this - it's 10000000% proven that really good roller-coasters are the best thing theme parks can buy in terms of ROI. Adventure World proved this. Many, many other parks proved this. Parks like Luna Park & Sea World in particular need to stop building middle of the road chaff and build something worth visiting for.