Understanding spam comments

Hello everyone,

I am operating a blog, and usually any form of spam is successfully blocked via Askimet. However, sometimes it does not work, and I am receiving the following types of comments on almost every single post within an hour or so:

Sender: jocfopfnfn
xhjedhacqneq.com/
[email protected]

Message: b4QhJb webgzfcfacwf, [url=https://zazttaihfluy.com/]zazttaihfluy[/url], [link=https://mipyedqvwvgw.com/]mipyedqvwvgw[/link], https://joeaqsncjwur.com/

I am just wondering, what is the motivation for someone sending such spam? The message does not contain keywords, or references to existing websites or products. It is completely useless, except that it is irritating as hell to the webmasters.

Thanks,
Aleks