First, one point needs to be clearly stated. Malwarebytes is not an antivirus program; it is an anti-malware program. And, Malwarebytes, at least the free version, does not run in the background. So, that fact that Malwarebytes found undesirable objects does not mean that Norton isn't doing its job well.
i wonder why people recommend me to go for free Avast antivirus free addition + Malwarebytes free addition instead of Norton.
Most likely, the reason is simply that they just prefer to avoid paying for antivirus protection if they can get free protection. And, regarding the use of Malwarebytes free edition with avast, I, like many other users, would use Malwarebytes in combination with any antivirus program. Again, Malwarebytes is not, per se, an antivirus program; Malwarebytes and other malware detection/removal programs such SuperAnti-Spyware or Spyware Blaster can, and should, be used in conjunction with antivirus software, regardless of what antivirus software you use.
NOTE: Keep in mind free versions of any program are usually limited to personal, i.e. non-business use; using them on computers used for business purposes is a violation of the software license agreement.
I have avast Antivirus Free and Malwarebytes free edition on my laptop. The laptop came with Norton Internet Security and I thought Norton was quite good. But, when the trial period expired, I elected to remove Norton and install the free version of avast, which I was already using on a desktop system. Again, the choice is a matter of preference. You generally do get some features with paid versions of software that are not available in free versions and some users, like me, feel comfortable using the free version. So, since you like Norton, I see no reason to suggest switching to some other antivirus, whether its free or not.