Why not to sell you HDD or SSD with your computer

[NikKlaus]

but not if you know what you're doing and using professional software

What is 'the way' then?
I've been under impression that overwriting data with other data makes recovery impossible.

you can have (almost!) all data ever written on a HDD/SSD recovered by professional data recovery services. It's done in a clean room and isn't cheap

like 9 years ago,i asked a for recovering some data on my old hdd and in 2TB data they asked me like €5K,from that time one started making backups properly.

Back into the topic unless you destroy physically the hdd/ssd if you have data that is sensibile they will always recover it imho.