Because the “days” of the Creation are NOT 24 hour days!!!!
Man goes to God and asks him “What’s a million years to you?”
God replies, “A second.”
Then the man asks God, “What’s a million dollars to you?”
God answers, “A penny.”
Then the man asks God, “Can I have a penny?”
And God answers, “Sure, just give me a second.”
Think about your certainty of that statement. Compare to Genesis, where it says "The evening and the morning were the FIRST day." Genesis then repeats the sequence 5 more times, evening and morning are the second day, and so forth.
The writer specifically called out one solar day, evening and morning, and then uses a specific count, of first day, second day, and so forth. Unless the earth's rotation has dramatically sped up, there is no reason to suppose the day was longer than our 24 hours. There is also no room for any other days prior to this, since on the FIRST day God made the heavens, the earth, and light.
Now, if you prefer to not believe it was 24 hours, and perhaps XXX years, that's your prerogative. However, you are the one at odds with recorded scripture, and are trying to force a compromise to fit with the required evolutionary time frames.
If you would assert that a day was really a thousand years, then the plain reading of scripture, of an evening and a morning were the third day would reuqire plant life to be in the dark for 500 years. Seems a little absurd, but again, believe what you want.