That's not really true, since all that I know of come with spacers for changes. My ISP giant could take up to 2cm of spacers.

That said most lower level pro and elite teams use standard seat post models of high end bikes due to transportation issues.

Having had a couple of ISP bikes I've gone back to standard seat posts because it does indeed seem pointless to me. The difference between an ISP giant and a version with a similarly shaped extractable post is at best modest. I've seen issues with a couple of different bikes with the head sitting properly once the clear coat underneath wore away. Saddle changes can increase to a significant height difference, and if you have any concerns with resale, unless you're tall, it can hurt your ability to sell.