[fmajid]

You'd be surprised how many top websites (e.g. Amazon, eBay) don't even implement HSTS, let alone HSTS Preload. Here's some naming-and-shaming:

https://blog.majid.info/hsts-preload/

[zamnos]

HSTS is a commitment to future downtime for your site, and as such, is not recommended if you care about uptime for your site (like, say, Amazon.com might).