Yeah, usually, though when I tried to sign up to Doordash my account already had someone else's details filled, and even though I corrected them to my details, I could never place an order; Doordash had pre-banned me. Many calls to customer service couldn't fix it, despite promises each time.
Now that I'm aware of this security flaw, I'm not sure whether that instance was incompetence or malice.
I've occasionally let my curiosity take me down the rabbit hole, to see if I can figure what it's all about. In one case, the email reminder about an upcoming job interview gave me enough to call the recruiter, and ask if they have alternate contact means for the interviewee. Apparently yes, there's a phone, so I suggested that they use it to ask them for their real email address.
Also, if someone uses my email to sign up for some site, you know I'll be using the password reset functionality immediately, then checking that site out ASAP.
Now that I'm aware of this security flaw, I'm not sure whether that instance was incompetence or malice.