Funny Money

I just though about something when I deposited they check I got for $100 into my bank account. For starters I was told it might take 3 day's for the check to clear. No biggie. I did ask if they could check if the check was good. a few keystrokes and yes the check was good. it was drawn on "BoA" who were right next door to my bank. I tried to cash the check over there but because I am not a costumer the wanted $5.00 from me
I was not about to pay 5% to cash a check, didn't needed the money that bad. Anyway Icalled my friend that night and I was mentioning the bank policy of charging non costumer $5.00 to cash a check. He stated that he thought I had the money allready because it allready not available to him. so I logged into my account...Nope not in there yet.as a matter of fact it took the full 3 days to turn up in my account. Now I have a stupis question. Were did the money go? were did it spend the 3 day's as I said I could have walked over there in 3 minutes.
 Money is earning interest so everybody is telling me, save it up and it will grow, well not my $100 for sure. It won't have enough time to breathe when it hits my account and the interest NOT earned in those 3 day's amount to $0.0123 Cents at 1.5% interest. So whats the big deal. Remember your grandpa telling you "a Penny saved is a Penny earned" Imagine this is not only MY $100.00, yours to and some other 2 million bank costumers at the same time. those $0.0123 turn into 24,600.00. Now were talking about real Money. pretty good company for my 100 dollar bill to keep don't you think? but now come the 60 million dollar question. Someone is paying this "extra Money" the one "holding" it hostage for 3 days? and if so
why doesn't he/she pay ME. its my money in the first place, my bank is just a custodian. They are Making money on my money when it is in my account. There is no physical contact with my check involved, Deposits are allways free.  so were is that xtra Penny