One reason I like competitions is because they have deadlines. Every year, the Age Short Story Competition acts like a carrot for me. Can I write a new story before the closing date? Often it happens simply because I've been thinking about it and the urge gets too much. With poems, I'm writing them on a fairly regular basis but sending them out doesn't happen often enough, so when the MUP competition closing date loomed, it was the impetus to look at what I'd written recently and send it off.
I often talk to students about competitions because they ask questions like, "Why do you have to pay an entry fee?" or "How can you be sure it's genuine?" Good questions. For a reputable competition, the entry fee usually goes towards funding the prize money and paying the judge. (Any competition with a goodly number of entries to read that doesn't pay the judge isn't playing fair.) But you will see some competitions where the first prize is $100 or $200, and the entry fee is $10. Whoa! Someone is making a nice profit. Those are the ones I tell students to avoid - and $10 is a lot for a student anyway.
Some competitions aren't competitions. The International Library of Poetry is one (there are several like this, including one that targets schoolkids) - they often don't charge an entry fee so they look genuine, and the $1000 first prize - sometimes bigger than this - is enticing. But what they do is publish the "winners" in a book. And everyone is a winner. The catch is you have to pay for the book. It's usually around $70+. It's cheaply printed, they cram as many poems in as possible (hundreds and hundreds) and sell it to the people whose poems are in it.
Now for many poets who haven't been published before, and may not even know of the many poetry magazines around, this is a thrill. They will say they don't mind paying the $70. Some buy more than one copy. But if you take a minute to do the sums, you'll see the problem. These books cost around $5 to print overseas somewhere, and even if only 70% of the people in the book buy one copy, that's a $65 profit per book. Sell 500 copies and you just made $32,500. And trust me, from what I've heard from people who've been caught out, this is a conservative estimate.