I have my mail server on a ISP for private email, but other ones email accounts for other purposes as well.

Yes you are right about your remark, but as I said, I am lazy and rather have Google servers do spam filtering and email aggregation than doing it myself with SpamAssassin.

I got to a point where I rather spend evenings with family and friends than coding.

... but gmail doesn't do spam filtering on messages it pulls with POP.

Yes it does, my SPAM folder is a living proof of it.

99% of those emails stay on my other email accounts when I disable pulling services.