Seven men have retired from the first round - on day one, Victor Troicki quit after just 20 minutes.
That brief stay was beaten overnight, when Serb compatriot Janko Tipsaervic quit his match after 15 minutes.
First round losers all receive $US60,000.
There is a rule on the main ATP Tour, but not at the Slams, that an injured player can give up his place to a "lucky loser" from qualifying, while keeping the prize money.
The thinking behind the move is to preserve the integrity of a tournament and prevent fans from feeling short-changed.
But Federer does not want to see the Slams opt for the best-of-three sets format, rather than the traditional best-of-five.
"I hope it doesn't happen, but I believe that more players clearly would finish their matches," said Federer, who is bidding for a record eighth Wimbledon title.
"A player should not go on court, if he knows he should not finish. The question is, did they truly believe they were going to finish?
"If they did, I think it's OK that they walk on court. Otherwise, I feel they should give up the spot.
"The ATP has adjusted its rule. Maybe the slams should have a look at what they could do for the players to make it just a little bit easier."
Federer believes that players who insist on competing in the first round, despite obvious physical ailments, should not necessarily be damned.
"For some, they just want to be out there, because they feel like miracles happen - maybe the other guy retires, or maybe the other guy is carrying an injury," he said.
"If I win, I have a day off, maybe I will feel better on Thursday. All these things play into the equation as well.
"Don't forget those things as well - could be rain, come back the next day. You never know what the player's motives are."
Djokovic said he backed the ATP rule being used at the Slams, but also refused to criticise opponents who fail to finish.
"If you walk out on the centre-court, there is a responsibility," said the Serb. "I'm sure they tried their best, but it is what it is."
American John Isner said players owed it to the fans to stay and fight on court for as long as possible.
"If it's excruciating pain, OK, you can't play," said Isner, who famously played an 11-hour match spread over three days to beat Nicolas Mahut at Wimbledon seven years ago.
"If something is tweaked here or there, and you feel like you can give it a decent go without hurting yourself, I think they should stay out there and I think you owe it to the fans.
"I know the Wimbledon centre-court didn't get their money's worth today. That's for sure."
Tipsarevic insisted that, with $US8 million won in his career, he didn't need to play for the $60,000 he earned for quitting his match when 5-0 down against Jared Donaldson.
He said he was given the all-clear by doctors to play, despite suffering searing pain in his hamstring.
"Lots of players fight through Challengers to get to the main draw of a Slam," Tipsarevic said. "They have to pay coaches and their teams."
"They get the chance to earn [$60,000] and I don't think anyone has the right to judge them, because the same guy may then go on to a Challenger and make just [$450]."
