Here's why:
* "Do" and "does" are helping verbs: They help the main verb in a sentence.
* The main verb is the action: It tells what the subject is doing.
Here are some examples:
* They do eat breakfast every morning. (The main verb is "eat")
* They do play soccer on the weekends. (The main verb is "play")
* She does like pizza. (The main verb is "like")
Important Note:
* "Do" is used with the plural pronoun "they" and the plural forms of verbs.
* "Does" is used with the singular pronouns "he", "she", and "it" and singular forms of verbs.