Spammers on MTA

[Topo1st]

For years I've been wondering, what's the point of joining a server, then spamming the server chat with nonsense like "yxxcvbn,ùmlkjhgfdsqazertyuiop^$qaaaaqqqqqqqqqqqqqqqqqqqqqqqaqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq" (real life example) and quitting fast. Are there any known spam bots disturbing MTA servers and therefore should us server owners start adding captchas to our login/registration panels (provided that a player cannot send chat messages until they've logged in)?