The singer refused the opportunity to top the Pyramid Stage bill as she doesn't feel comfortable playing to large crowds.
"She knows that we want her anyway, but she doesn't want to do a thing our size," Eavis told the Metro.
"Going on the Pyramid Stage is a bit daunting in front of 80,000 people; it's a bit much really."
Eavis revealed that Adele was a frequent visitor to Glastonbury festival and likes to have fun at the event, rather than perform. He added: "She comes every year usually, and has her own little party."
The festival organiser previously confirmed that he has already booked the three headliners for next year's Glastonbury festival, but will not give any clues as to who they are.
Adele's second studio album recently passed the 9 million sales mark in the US and has sold over 18 million copies worldwide.
Watch Adele perform 'Turning Tables' live at the Royal Albert Hall below: