Because he earned it. He was even good enough to hold the WBA version of the heavyweight title but everyone knew who the " real " champ was.
Terrell turned professional in 1957. At 6'6'' he learned early how to use his height and reach to his advantage. He developed a good jab and learned how to tie up his opponents on the inside. It wasn't pretty but it was effective.
The Chicago-based Terrell won eighteen of his first twenty contests losing two eight round split decisions to Johnny Gray. In 1960 he was outscored by the capable Wayne Bethea and in 1962 Ernie suffered a major set back when he was halted by the powerful Cleveland Williams.
Undeterred, Terrell began his march to the top in 1963 defeating Williams in a return match and top contender Zora Folley. In 1964 Big Ernie beat Gerhard Zech, Jefferson Davis and stopped a young Bob Foster.
When the WBA stripped Ali of his title recognition they matched Terrell with perennial contender Eddie Machen. It was an ugly fight with a lot of wrestling and little punching but Terrell did what he had to do to win the " vacant " title.
Maybe Ernie was not considered the real champion but he did establish himself as the most formidable challenger to Ali. He closed 1965 with a decision over rugged George Chuvalo. And in 1966 Terrell defeated a slick Doug Jones.
Finally after a failed attempt Terrell and Ali were finally matched to unify the title. The bout would take place at the Houston Astrodome. Ernie's bold refusal to acknowledge Ali's Muslim name and refer to him as Clay irked Muhammad who vowed to punish Ernie. Punish he did as Ali worked Terrell over throughout the fifteen rounder.
Round after round Ali would lash out at Terrell with punishing jabs and flurries while screaming " What's my name?" To Ernie's credit he gamely absorbed the punishment with a very swollen eye. When it was all over there was no doubt who the King of the Heavyweights was.
The WBA would later strip Ali of the title again in 1967 for refusing induction into the Armed Forces. An eight man elimination tourney was set up to determine Ali's successor. Ernie was one of the eight contestants and an early favorite to win the tournament. But Terrell was eliminated in the first leg of the tourney after being upset by Thad Spencer.
Terrell looked to be finished when he next lost to Mexican Manuel Ramos. He would not fight again until 1970 and his comeback drew little interest until he scored a major upset in 1972 by halting highly rated Jose Luis Garcia. In 1973 Ernie lost a very controversial verdict to Chuck Wepner but his career then came crashing down when he was belted out in one round by Jeff " Candy Slim " Merritt.
In all, Terrell fought 54 times winning 45 of them. He stopped 21 foes. Ernie suffered nine losses but was only stopped twice. Today Ernie is remembered as a footnote to Ali's pre-exile days.
But in reality he was a viable contender who was overshadowed by " The Greatest."