Why do states like California and Arizona insist on taking days or weeks to count their ballots?

The longer it takes to count the ballots, the more suspicious people become about the results.

Now I am not sure if one hour is enough time, but the idea is that these ballots could be set up and ready to go by the time the polls close. Yet, many states (such as Pennsylvania) decided to not start counting them till after they had counted all of the in person votes. This seriously makes no logical sense at all. In fact, I am not sure what excuse these states came up with to do it that way.

My thoughts have always been the same. These states and the counties within these states who insist on taking their time are hoping to be in a position to possibly change the results of the election. As the old saying goes. Just tell us how many votes we need and we will make sure to find them. Can't do that if you do not know how many votes you need.

But none of that explains how California can still not have races counted 2-3 weeks after the election or why Arizona counts their ballots over several days rather than on election night. There is only so much time it will take for the post office to deliver ballots that are post-marked on election day. Ballots not post-marked on or previous to election day do not count.

Anyone have any ideas why it takes so long?