Thanks for playing and thanks for the feedback! I noticed that too after playing a bit more and sharing with friends.
The only difficulty escalation right now is the falling block will fall faster as you get more points, but since there's so much space, I doubt you'd ever notice.
Planned updates:
Every few turns, you'll be given a warning like "New Row in 5 Turns" and then a row will spawn at the bottom -- not every column, but an escalating percentage. And then you'll have fewer turns until new rows spawn in a cycle. So might by 5 turns at first, then 4 the next time, then 3, and finally go back to 5. That should add some pressure. And when new rows spawn, the range of values will get expanded, so it's less likely a new rows helps you.
Mostly, trying to find ways so it's not empty space all the time. Too easy to clear the whole board and never risk hitting the fail state (not being able to place the falling block in the play area--just like Tetris.