I suspect that you're going to catch some grief for this statement. :)
As an internal engineer, when an internal ticket comes in I'm going to track down the issue, may realize it's a known thing that requires a lot of planning to resolve, loop in my manager, etc. but ultimately it usually ends with "we don't have time to address this right now and it doesn't affect enough users". If you're lucky there's a workaround that can be shared.
Now, I don't like that. I'd rather fix the issue for the user but I already have committed deadlines and team goals and it's rather easy to just go with a "sorry, we may revisit in Q1 or Q2 next year".
The support agent still has to a) deal with the customer's anger and b) cannot be honest with them, i.e. needs to wrap the situation in a blanket of corporate speak so as not to shed a bad light on internal teams / the company. At the end of the day they are just powerless and have to take on the responsibility in front of the user, whereas the engineer may feel unsatisfied not being allowed to spend time on it, but ultimately is far enough removed from the user to be actually affected by the situation. Granted, personally I always try my best to get a fix out but a lot of engineers would rather work on their projects and the managers want that too.
FWIW, when I did customer support I always reminded myself that nothing is personal. When I'm at the opposite end (a customer) I also don't get mad at the individual I'm dealing with unless they are not trying to understand or help at all.
Funny thing is I used to take things personally and it did occasionally lead to me going the extra mile to save the situation, but it is just so emotionally exhausting, to the point where I do not think it is humanly possible to maintain that level of service (I suppose some one might be able to, but I have not met anyone like that).
A part of me misses that do-or-die personal commitment to the customer, but for the most part I enjoy not going insane
Reader, working in customer care blows. It sucks hardcore. From my engineering work, I actually knew what the cause of the problems were and understood the timeline for fixing them -- information that real customer care reps rarely have available to them, but even that wasn't enough to appease some people. Even when people weren't rude, just the never-ending barrage of complaints and problems that I had to fix wore me down. And I only worked one shift, and then went back to engineering the next day.
People who can do this day after day, retain their composure, and somehow not burn out from the nature of the work are awesome, and they have my respect. Their jobs are absolutely more difficult than mine.