The paid ad placements you see are the freest of markets. If your competition has a better mousetrap you will lose in the long wrong.
Landing pages are a numbers game and one of the most important aspects of your sales funnel. The percentage of leads or sales you convert from paid traffic has a huge effect in terms of dollars for your campaigns.
A large scale campaign can mean that a 1% increase in conversion rates translate into tens of thousands of dollars to your bottom line.
If your competition has worked and evolved their campaigns into a profitable venture with a certain ROI in place then they will have more to reinvest to protect their place in the market. If you are both selling something with a $75 profit and they are acquiring them at a CPA of $45 and you at a cost of $55 then you can expect them to compound the effect with higher bids and better positioning in the future.
You CPA is a formula that is effected by the conversion rate of your landing pages among many other key factors. If you both pay $2 per lead on 1M leads and convert them into customers at a different rate then your competition is turning more profit and can reinvest in the form of bids. They will maintain high positions and more exposure and get better quality leads, expanding their lead on you in profitability.
Conversion rate from a successful landing page goes up and pushes cost per acquisition down and increases overall profitability of the campaign leading to more to reinvest to expand and compound their advantage on you.
Make sure you set the dinner table before you serve dinner. Your landing page is the one part of the math formula that you have the most control over. As you conversion rate goes so does your ability to bring people to it to convert. Invest in it first and always take advantage of this very easy to manipulate part of the math formula and bottom line.
This is NOT an ad for unbounce, I just grabbed their image as a leader in the industry and example. That said, they are a great place for anyone to learn and improve their landing pages.