grammar - "While" and "When" phrases in the future tense

When I am using the future tense, why do "while" and "when" clauses have to be in the present tense?

For instance,

"While I am eating you will be speaking on the phone"

and

"I will be waiting when your plane arrives"

Both sentences are grammatically correct.

But, doesn't it make more sense to say

"While I will be eating you will be speaking on the phone"

and

"I will be waiting when your plane will arrive." ?