By not having sequential dates, you don't have to make the show a serialized format- same as a lot of westerns. The Rifleman had 3 things: the faster than a pistol gunslinger--hos young son; and, when in town, the Marshall. No matter how beat up the hero was, he would be 'good as News' the next one.

ST=same thing. Since Earth time means nothing off earth, you have a ship board chronometer, but that's it.

After ST:TMP re-established everything, there was one other thing to deal with--the fans, and especially the actors were OLDER. Their tanks and positions were different, so then you have to establish a timeline to explain this, this 'In the 23rd Century. It started us all at the same point, and future writers had a 'jumping off point'

So, Batman avoided that situation (even tho he came from the 1930s), by emphasizing that he is HUMAN, which gives him emotions, which makes him unpredictable. But, almost every version of his origin story has to br from a different universe, because of all the changes in him, and the criminal gallery that opposes him. So, even in each of their areas, (TV/Movies/Comics), there's till have to be in different universes. The original cartoons and the Adam West /Michael Keaton versions, are the original canon. Then, Tim Burton and others wanted to bring him up to now--so they make him moody, depressed, angst ridden, so teens will see him and say that they see themselves in him.

Look, Superheroes were NOT supposed to be realistic or hyperrealistic--theyare supposed to be fantasy. Why do I want a Batman who matches what people see today? I'm trying to escape that. If I want guilt, vengeance, anxiety, I 'd watch politics

The problem with DC (and, I STILL think Christopher Reeve (rest in power) is THE CANON Superman (I'll fight you on it). But, these characters were conceive a certain way, and fleshed out fully 70 years ago!. When you make hero God-like, there is nowhere to go. Put Superman in most Marvel movies, and they are done in 10 minutes (sorry Thor, even you don't have all those skills). They used to have Shazan!/Captain Marvel in there, and he was the only hero about equal to Supes.

1. The batman comics have rarely even matched the TV shows/movies, except for character names, basic personalities, and the overall framework, (the same issue as Superman), so, saying they are canon is questionable.

That is why Star Trek used the 'multiverse' idea (used in soo many comics), to justify the 3 Chris Pine 'Kirk' movies, by putting them in an alternate universe. And, to not even show it happen, until they brought Spock canon in to explain.

This gave them the ability to have Pine's Kirk and other main staff behave differently, and have a different backstory than Kirk canon, thus avoiding the wrath of the fans.

Instead of the fans saying "OH my God, they're destroyed MY Star Trek, they could say, "This was pretty good, but not my show.

It also gave new viewers not familiar with ST the ability to come in, and not have to be told hours of exposition so they can understand it.

When it comes to actors, a lot of things go into a desire to retire or semi-retire.

1. Money. After years on 3 major shows, he likely has enough money to retire;

2. Because of so long on TBBT, he might have found he was stereotyped in that role;

3. A lot of actors don't like to revisit roles they have done, especially for as long as he has, and, except for paid appearances in non-series reunion.