Also consider that data isn't timeless. Data about your habits now, are outdated and close to worthless in a few months. So, reducing your data footprint always has an effect.
Also, consider that data isn't necessarily properly associated with who you think it is. I often see suggestions that are clearly due to my wife's browsing on her own computer (which is nearly identical to mine in terms of browser fingerprinting). Obviously we have the same IP to the outside world and we share some interests, but not everything!