why radha ji and shri krishna didn't marry

Radhe radhe all,

We all know Krishna left vrindavan at the age of 11 years.
All the Gopi and Radha ji had this deep,eternal love for shri krishna.
Infact all the Gopi's had their different husband but radhaji never married.
(although i read on internet that radhaji also had husband like other gopis, but i didn't find any such mention in Shri Mad bhagwat)

Now, the question is why Krishna and radhaji didn't marry.
Infact Krishna had over 16000 wives, so why not one more?
We all know marriage is a bond which happens between two persons.
Radha and Krishna are not two people, they are one.
So how can marriage happen between Radha and Krishna.

I am quoting one conservation between Radhaji and Lalipa Gopi from shri mad bhagwat:

ललिता गोपी ने श्री राधिका जी से पूछा - आपका और श्री कृष्ण का क्या नाता है?

राधा जी ने कहा - ललिता, तूने जो मानना हो मान ले ।

ललिता जी ने कहा समझ गयी - आप श्री कृष्ण की प्रियतमा है और वो आपके प्रियतम है ।
राधा जी ने कहा-
तू कुछ नहीं समझी ।
हम दोनों में प्रियतमा और प्रियतम का भेद है ही नहीं ।
बस मिलन की तीव्र जिज्ञासा-अभिलाषा पैदा होती है, जो हम दोनों को पीस कर एक बना देती है ।
ये प्रेम की प्रगाड़ता(गहराई) है जो राधा को कृष्ण बना देती है और कृष्ण को राधा बना देती है ।



Lalita Gopi to Radha: what is the relation between you and Krishna?

Radha: Lalita, you can assume whatever you want.
Lalita Gopi said: ok, i understood. you are her beloved and he is your beloved.
Radha ji said, you didn't understand anything.
There is no concept of beloved between us.
there is just intense curiosity to meet each other, which makes both of us a piece.
This depth of love, makes radha into Krishna and Krishna into radha.