I agree that in most of the stated is no profit, and that in some cases financial loss may occur. However, most beginners choose these methods because most of them do not require any initial investment. Although the posting of ref links in the forum is prohibited in posts (with some exceptions), the promotion of ref links in the signature is allowed. If something good is promoted (hardware wallet or crypto exchange), it's not a bad source of income (at least not in some poor countries).

For example, if someone promotes their Ledger ref link, they will get 10% for each sale which is $6.5 for each Nano S, or $16 for current Ledger Bundle Pack (S+X model). For those who create their own web pages and know how to promote them, affiliate business is one of the options how to start making money.