These days if you want the lyrics to a song that information, as is all information these days, is easily obtained.  This however wasn't always the case.
    In the days before the internet the only way to get the correct lyrics to a song was to buy the sheet music from a music store.  This was something only professional musicians did. 
    The rest of us would try to decipher the lyrics as best we could from a crackly AM radio.  Rock singers are infamous for slurring and garbling their words.  John Fogarty of Creedence Clearwater Revival is one of the worst offenders. Prior to the internet the only Creedence song I understood all of the lyrics to was Suzie Q.  Here's just one small example of countless others.  In Green River Fogarty sings "Flat car riders and cross tie walkers."  For decades I heard "black on righties and cross high waters."
     Sly and the Family Stone's lyrics were often as difficult to comprehend.  Again, this sounds stupid now, but back then NO ONE knew the proper lyrics to songs.  We all just did the best we could.  In "Dance to the Music," a great song, the first verse is easy enough to understand.
All we need is a drummer for people who always need a beat, yeah!
The next verse sounded like I'm gonna add a little bird talk and make it easy to move your feet.  It is actually I'm gonna add a little guitar and make it easy to move your feet.
I'm gonna add some bottoms the help the girls with a just one eye = I'm gonna add some bottom so that the dancers just won't hide.
You might like to hear my organ, I said it's my kind of guy = You might like to hear my organ, I said him Ride Sally Ride now.
   If I could hear to the Horned Toad, Cynthia on the drums = if I could hear the horns blowing, Cynthia on the throne.
Cynthia girl has got a message that says All is well, call out = Cynthia and Jerry got a message they're saying, all the squares go home.
     As difficult as it is to imagine now there were countless Rock songs that none of us knew the proper lyrics to until the 90s and the advent of the internet.  But that didn't stop us from singing them.  No one could call you on your improper lyrics because no one knew for sure.  Anyone born in the 80s or prior knows exactly what I'm talking about. 

https://www.youtube.com/watch?v=Jn2PNlhvy8E

    Even Jimi Hendrix would fake lyrics he didn't know for sure.  In his cover of "All Along the Watchtower" by Bob Dylan Hendrix gets very creative with one line. 
Business men they drink my wine, plowmen dig my earth,
None of them along the line, know what any of it's worth.
Those are the proper lyrics.  Listen to what Hendrix sings at around 0:45.  It's obvious that he doesn't know the lyrics.
https://www.youtube.com/watch?v=TLV4_xaYynY
    Oddly enough this doesn't detract from the song at all though it should. 

   Lyrics printed on album sleeves could be helpful but...  most kids didn't have money for albums. I didn't own many until my older teen years when I was working.  And you're certainly not going to have the album for every song you hear on the radio.  Also a lot of music was on cassette or eight track.  So even with lyrics often but not always printed on album sleeves there still was a lot of confusion about the proper lyrics to popular songs.

Jimi Hendrix again, Purple Haze : " 'Scuse me while I kiss this guy".

Sometimes words can't be understood because they literally are gibberish. 

https://www.youtube.com/watch?v=_g6YxkSqL20

Your perception is exactly correct.  My dad pointed me to that song a while back.  It's by an Italian singer, but he wanted to do a song that sounded like English.  That's what came out.  Was a huge hit too. 

    Here's an oldie with badly garbled pronunciation that I never understood the lyrics to until fairly recently.  Amazon Music posts the lyrics to every song they play so they came to me accidentally.  It's A Long Cool Woman in a Black Dress  by the Hollies.  It seems like he's deliberately trying to make the lyrics unintelligible. Try to decipher the lyrics without cheating.  Good luck.

https://www.youtube.com/watch?v=g8XiNKsKyVk

https://youtu.be/gavcjNniIvk

Pretty much every single manic Street Preachers song is just random gibberish.

You could understand it if he was singing in Welsh, but I think it's supposed to be English.

@zud
Hot dog jumping for Albuquerque

Doesn't make any more sense, and I think that's the actual lyric.