As low or a human as I think Canseco is, I do believe him in that a LARGE percentage of players at the time he and McGwire were using were also using steroids. I also think that players that wouldnt have normally used were pressed to use because a guy that was young and roid-built was gonna take his job unless he upped his game. That is the competitive nature of those in professional sports. They are setup up for life because that is what we wanted to see. We wanted to see McGwire hit all those homeruns. Had we never been told that they cheated, we would have been blissfully happy. However, we all knew that these guys were too big, too different from when they first joined the league but we loved to watch them hit the home runs and we turned a blind eye. We are now enraged that they cheated...but really...didn't we know something was wrong? I mean...look at Barry Bonds! His head grew many sizes, he got taller, hey doubled his mass nearly from when he first got in the league.
Baseball players have been using all kinds of things to get an "edge". Greenies (amphetamines) have been around long before steroids and were used by many. There has been no witch hunt for greenies users and if they told the truth we would be shocked at how many of our heroes of the past that we thought were squeaky clean used them. Steriods were the next step beyond greenies.
These guys have a limited window where they will likely be a pro athlete. As far as looking for the future, the immediate payback to extend even just one year of a pro career is pretty attractive and can pay millions. So I don't think they are giving great consideration to 20 years down the road after roid usage...I think they are thinking about extending that career or padding a career with more stats.