I could be totally off base here, but in the olden days, lefties primarily threw their hook down the left side, near the gutter and
curved the ball into the pocket. Righties generally started in the middle of the lane, or even left of center, threw the ball out to the right and curved it back to the right side pocket.
Is that true today? and if so, why?
Since there is less oil on the first few boards, both left and right side, why doesn't everyone throw near the gutter to avoid the
oil ?

I'm sure there are right-handers who try to play straight up the outside as well. The problem right-handers face most often is simply that there are more right-handers, so the outside boards tend to dry up quicker on that side than they would for left-handers, so right-handers have to move inside to find the oil, bouncing it off the dry (which we like to call "the wall", especially with most house shots) so that the ball doesn't hook left of the pocket.

Also, the "Track" you remember (the worn part of the lane around the second arrow for right-handers) still exists, although it's probably less pronounced on today's synthetic lanes than it was on the old wood lanes.

Well, only a very few will play the guttershot. I am comfortable with the shot but I don't used it unless it is an alternative.

Part of it is as Richie mentioned, there is normally more traffic on the right side. In the "olden" days the left side might have had more oil on it, if this was before the modern lane machine. You will still see some lefties playing straight up the boards near the gutter, but only on higher amounts of oil, or using really weak or older equipment. They will normally be able to not have to adjust as much unless the pair is loaded with lefties. If you watch the PBA telecasts you will see many of the lefties still playing outside of 10, with Jason Couch or Rhino Page, both with a little more power than the others playing a little deeper.

As for playing near the gutter and avoiding the oil, today's equipment needs the oil, if not it will hook up too soon, and either roll out or over hook. Plus too much friction really wears on the Track of the ball.

The other reason that righties played in was because of the Track. It was an advantage and a disadvantage. You can't play out with the Track because if the ball hit it, it took off. You could however play in and get some recovery due to the Track.

I have never played a house shot where there was enough oil outside of 5 to lay down anywhere near there. Even lefties, on most house shots, tend to play the "Track" kind of line, at least from what I've seen. On sport shots, it's a different story, and both lefties and righties can play outside. However, most bowlers are used to the house shot and can't/won't go right, so I always try to. Having a line to yourself is nice.

Most righties won't play out there because there isn't enough oil for their balls and the ball either grabs the lane to early or they don't have a ball for dry oil ball.

I'm not sure what era you are calling the good old days, but before the urethane ball hit the lanes, there used to be oil from gutter to gutter. Due to the fact that there were more right handers than left handers, the right handers tended to play around the second arrow where the lefties needed to create more angle because there were fewer of them to dry the lane out enough to get a good reaction, so they played out near the channel.

With the modern house shot, drying the boards outside of the second arrow and placing a river of oil in the middle to help keep errant shots in the pocket, the lanes have to be played from the second arrow in on both sides of the lane unless you are lucky enough to have a place that puts a crown oil pattern down. A Crown is where there is still dry boards outside, but only after the first 20ft or so, between there and the foul line there is oil all the way across the lane, from the gutter inward the oil gradually increases and gets longer down the lane.