The men's and women's circuits, which run across 11 months with extended formats at several tournaments, have come under fresh scrutiny during the "Asian swing", where extreme heat and humidity contributed to a spate of injuries and withdrawals.
The Professional Tennis Players' Association filed a lawsuit against the sport's governing bodies in March, calling the scheduling situation "unsustainable".
After winning the Tokyo title last month despite playing with an ankle injury, Alcaraz withdrew from the next event in Shanghai, saying he needed time to recover.
His decision to play in the Six Kings Slam, which offers a reported $1.5 million in appearance money with a winner's cheque of $6 million, stoked plenty of criticism from fans.
"It's a different format, different situation playing exhibitions than official tournaments, 15-16 days in row, having such a high focus and demanding physically," six-time Grand Slam winner Alcaraz said.
"We're just having fun for one or two days and playing some tennis, and that's great, and why we choose the exhibitions."
Last year's champion Jannik Sinner is also playing in the Riyadh exhibition event following the world number two's early exit in Shanghai due to cramp.
"I understand (the criticism), but sometimes people don't understand us, our opinions," Alcaraz added. "It's not really demanding mentally (compared to) when we're having such long events like two weeks or two and a half weeks."
Alcaraz, who received a bye to the semi-finals and takes on Taylor Fritz later on Thursday, said his ankle had still not fully recovered. "I don't feel 100% and the doubts are there when I'm moving on court, but it has improved a lot and I'm going to compete and perform well in the Six Kings Slam," he said.