I doubt very much that it's been like this for 100 years. In 1900 there were 413,000 people living in Oregon. More than 105,000 people lived East of the Cascades, Deschutes county's population wasn't listed so it was higher than that. So say roughly 25-30% of the state lived on the East side.
Today, there are 3.7 million people that live in Oregon. Half a million live on the East side today. About 13.5% of the pop. live there now vs. 25-30 percent 100 years ago.
I also doubt that every single resident of Portland come and hunt Eastern Oregon every year.
4-5 years to get a tag? With the exception of South East Oregon, you can draw most deer tags with 0 or 1 point. There are a bunch elk tags that you can get with only 0-1 points also, maybe 2 points. Units such as Desolation, Catherine Creek, Minam, Sled springs, Pine Creek, West Beulah, Malheur all have about 50% draw odds. Heck Minam is underscribed! 100% draw for first or second season high country wilderness hunt! The unit I love to bowhunt in I could rifle hunt every other year if I wanted.
Sure ya some of the tags I want take 4-5 years too, they are good hunts. Some of the tags I want take 10 years or more! And they're bowhunts! There are options if you want to rifle hunt every year.