Many of you are disgusting.

Why?

Because you hijack your customer's DNS, meaning that they have no control over it.
It also raises the risk associated with doing business with you just because you want a little convenience.

If your cloudflare account is compromised (that's where many of you move the NS records to), then multiple customers will be affected, and could result in a massive compromise.
Not only web servers require DNS records - A correctly configured mail service requires a bunch of records, including SPF, DomainKeys (Multiple), DMARC, MTA-STS (Multiple), TLS-RPT. There is also a need for the customer to add authentication TXT records among other things from time to time.

Just stop it.