Lines are there to help to see the change of direction. Trend lines are drawn from market graph low to low and high to high until trend breaks and retraces to confirm the break. As you can see theres no vertical lines for dates. Its just appoximate dates under the graph.
If you want to learn how trend lines are supposed to be drawn then you can google about it. Theres plenty of tutorials.
Of course you cant take any altcoin trends as serious trends. Its just another tool for predictions.
Common , we both know what I was talking about. If you would have drawn the first line from the random moment you chose till today , the marketcap line would be linear and would have shown no increase at all. .