Well, there are many possibilities as to why.
Normally, the table is broken like that because there isn't enough space for the next line on the original page, so the table moves it automatically to the next page.
Depending on what you want to do and what you are doing, you may be able to keep the table together by using the paragraph function. Select the entire table, go into paragraph (on the toolbar or up in the format menu) and set the "keep lines together" and "keep on same page" options. this will only work, of course, if the table doesn't go longer than one page even when all alone on that page.
It also will likely make the entire table move to the next page. that may work for what you are doing, or it may not.
Maybe increasing the page size under page setup will allow the entire table to stay on the same page too. or maybe you can go under the table menu and format the table so the lines have a fixed height, allowing the table to keep together. Or maybe change font size of the items in the table (make them a little smaller). A lot of options that could maybe fix your problem, but it is hard to say without actually playing around with it myself.