If writing didn't have paragraphs, it would be so much difficult to the readers. First off, if there wasn't paragraphs, there would be a big block of words to read without pausing.
The reader will also get bored because its too long. It will also be a problem because whenever theres dialogue, there must be a different paragraph for that. It will have the reader very confused at some point.
Hope this helps!
---Avery