Why did Queen Elizabeth did not have kids?

Answer 1

Because she never married. Granted that's not an absolute bar, but while it was more or less accepted that an unmarried King might have a few bastards, it was socially unthinkable for a unmarried Queen to do so.

So, why didn't Elizabeth marry? She was more or less engaged a couple of times, but nothing ever actually came of any of them.

There are several factors to consider:

Elizabeth's sister Mary had been forced to share power with her husband after marrying, and it's possible Elizabeth wanted to avoid that. (The same thing would happen a few reigns later to Elizabeth's distant cousin, also named Mary, though she at least seemed perfectly happy with the arrangement.)

Elizabeth had been in love with a childhood friend, Robert Dudley, but couldn't marry him: for one thing, he was already married, and even after the death of his wife, the nobles made it clear that they strongly disapproved of such a match and it wasn't out of the question that they might have rebelled against the crown had she married him. Elizabeth hated Dudley's second wife, and it's at least suspected she may have resented her for being free to marry the man she loved.

There was also other recent history to consider: had Elizabeth married and had a child, that child could have been used against her in a power struggle. Having been "a second option" herself with a valid claim to the throne, she was well aware of the unbalancing effect this could have; it's speculated that this is why she never formally named an heir. She was already having enough trouble with Mary (hey, it was a popular name) Queen of Scots, who was also considered a viable candidate for the English crown.

As well, Elizabeth was basically making bank on her status as a single queen: her marriageability was an asset in political negotiations with allies or potential allies, and courtships played a big part in her foreign policy.

Elizabeth may have been put off sexual relationships in general by Thomas Seymour, her ... step-stepfather (after her father Henry VIII's death, her stepmother Catherine Parr married Seymour, and Elizabeth lived with the two of them). Seymour's behavior towards the at-the-time 14-year-old Elizabeth was at the least questionable, and eventually she was sent away after Catherine discovered Thomas and Elizabeth embracing).

There's also been speculation that Elizabeth may have known or at least believed herself to be infertile.