While I can understand why people may want to change their gamertag on PlayStation Network, we have to acknowledge potential negatives to this feature being available as opposed to just looking at the situation from a positive side.
Advantages:
- You won't require to create an entire new PlayStation Network account to make even the slightest change to your gamertag
- If you wanted to prevent someone from contacting you over PSN who you had blocked (let's say they created new accounts just to keep sending you messages/invite spam) you would be able to change your gamertag and they wouldn't know the new one to contact you
- If you changed your gamertag you would still be on the same account therefore all your content is available there, whereas if you had to make a new account for a new gamertag then your purchased content would still be from the old account
- You would be able to change your gamertag to confuse your friends
Of course, there are many more advantages to being able to change your PSN gamertag and I cannot know them all, although everyone has a different opinion on which is a benefit and which is a disadvantage.
Disadvantages:
- If you changed your gamertag and then someone else happened to change theirs to your previous one then it may cause confusion (especially in the case where the previous owner of the gamertag had a YouTube channel or did something unethical and therefore people think it was the actions of the new gamertag owner)
- If there was a block on using previous gamertag someone else had owned (to solve the negative issue listed above) then they would get filled up quite easily and there would be less gamertag choices overall for other people
- There would most likely be a limit to how many changes to your gamertag you can make between a specific period of time, therefore if you used your last change but regret the decision then you'd be stuck with it for awhile
- If your account was targeted and happened to be hacked by someone else then they would have the ability to change your gamertag and make you look silly
Sony are more than capable of introducing the feature for gamertag changes into their network, they could have introduced the feature during the PS3 times or at the start of the PS4 release. However, they haven't - they will have their reasons for not adding this feature, and we can only assume that they are genuinely good ones.
Although, I'm sure Sony are focused on introducing more important and powerful features than a gamertag change right now.