Why are these noobs never gets tired in posting shits?
Bots don't get tired.
If these are bots then how can we stop generating new bitcointalk accounts which are being used as spamming/ bumping ANN threads? Investigating and Reporting can be an irritating routine if there is an endless registration of bots. 
Impossible to stop fully. Manually reviewing and whitelisting all new accounts would help and probably around 99% of bots would get caught in that trap then. A bit more work for staff but at least the forum doesn't become an eyesore and hopefully people will get the message that using bots is also a waste of time. Sadly, many bots are still slipping through the cracks and many of them even earn from campaigns, which is further reason why signatures from Juniors should be removed or at least make them require one merit to become a Junior which would help a lot in curbing abuse.