Trouble with long .mp3 files (one hour and so long) : they don´t start at the beginning when replayed... why?

[Ron Wolpa]

Some classic music .mp3 files I'm used to play on Poweramp are nearly 2 hours long. 
In this case on the meta tag track there is only one track number , that is track 01.
Usually symphonies and concerts are divided in movements , so in terms of files it should be this way too.
 I mean  each movement has its separate file and each file's meta tag  numbered with respective track number in ascending order.
As a matter of fact many folders I have with classic music or jazz  are organized that way.
 I have not trouble , no matter what else I play ( shorter files ! ), every time  I get back to such folders ,  Poweramp will start to play track 01 at the very beginning.
However I noticed that if I play long files  , supposing I play one of them until 37:45 , then  choose any other folder and play other  files  , as I 
get back to previous , the player will start not from zero but exactly where it had stopped (37:45).
Is there any explanation why it won´t start from zero ?