Not really the reason. Some of us are a little older and have followed tennis for a long time, long before Federer started winning anything. Why didn't Borg win the Olympics? Easy answer. It wasn't held when he was active. Why didn't Lendl? He never entered. Why didn't Sampras? He didn't try. Sure, he entered in 1992 - on clay. But he did not enter in 2000 or - most significantly - in 1996 on HC in his home country, where he would have been overwhelming favourite. Many of the other top players likewise gave the tournament a miss. Why didn't they play? Easy. Not worth their while. We oldtimers remember this all too well. While one concedes that its value have risen over time, it is a stretch to place a tournament that used to be no more than a paranthesis suddenly among the very top. Back in the 90s, the title of Olympic champion in tennis was about as meaningful as Olympic champion in football was and still is today.
Appreciate the response, but that explanation is quite telling isn't it? Times have changed big-time, nowadays all the top players enter, to not do so would be inconceivable now. And the most recent tournament being held at the hallowed grounds of Wimbledon made it that much more special, and it felt a lot more prestigious than in the past - granted it doesn't have the rich history of some of the other tournaments. There's absolutely no reason why it shouldn't be an enormous win, especially since it's only held every 4 years, I think only the attitude of the players has prevented that in the past, but it clearly isn't the case anymore. Just find it frivolous that know-it-alls on here suggest it's worth nothing, when luminaries of the game are clearly desperate to win it. That's far more telling as to the true worth of the Olympics.
Australian Open used to be regarded as pretty weak didn't it? But not anymore, because the pros all take it very seriously, a fit player choosing not to compete would be unthinkable. I think there's a comparison to be made there.