All of us received spam mails everyday. These mails are mostly advertising emails that sent to you without your pre-authorization or approval. They are often being sent in bulk, and targeted mass population. People or companies who are sending these type of emails usually intend to gain business/income with less effort or within a short time. This is obviously illegal and less moral.
I cannot be sure that if this is a shortcut to bring profits. But if you are a legitimate company or you really want your business to grow, never try sending this type of emails. If people do not like the email content, the mails could be marked as spam by them manually. And if many people do this, it will certainly change how the client’s mail filter behaves. The next time an email using the same domain or server is sent, the client mail server may automatically filter the email into spam mailbox. This doesn’t not only affect the existing email recipients but also to the new recipients.
Remember, any type of email will be meaningless if they are being filtered and not seen by the recipients. Sending spam mails not only can cause this long term effect, but also defame reputation.