This is what Lois Lane offers Clark Kent aka Superman aka Kal-El: The chance to be all those people. Clark is not just one person, he has multiple worlds in which he lives in, and Lois can offer him a life in each.
When he’s with Diana he is Superman. All super all the time. No time for Clark. Diana can handle that, Clark can not. He needs to be normal, because that is how he was raised. As Chloe in Smallvile said “He’s not god!” He needs to switch being super off, and rest. Or he’ll go insane.
When he’s with Lana, he can be super, he can be Clark, but not Kal, the meeting points between these worlds. He always hid from her. She knew he was Super, but he was still Clark all the time.
But the beauty if when he’s with Lois, is that he can be all these people all the time with her. He can be Super, he can be turned off but still talk about his day (and she’ll get it) or in the words of Wonder Woman herself, Lois can be his oasis away from it all.
That’s why he needs Lois. He is only one third of the man he can be in any other relationship. But with Lois, he can be the true Superman he is destined to be.
None of these women, Lana or Diana, as wonderful as they are can ever be Superman’s Lois, because there is only one god damn Lois Lane. And anyone thinking other wise is fooling themselves.