Birch wood flooring has always been a popular choice due to the fact that it is cheaper than oak yet is still a hard wearing wood floor with plenty of natural colour variation. It’s worth checking out some pictures of birch flooring online so you know what i mean. As you can see its very different to oak flooring, yet both of these floors are the most popular solid woods sold today.
I believe its a trade off. Simply price over product. Oak is hard wearing and long lasting, but more expensive. Birch is cheap flooring, that is just not as hard wearing (or beautiful) as oak. People choose it because of price. Maple would be a better option for a light floor instead of birch, as it is more stable and harder wearing but it does not sell anywhere near as much volume. And that means it is simply down to price.
Of course now that engineered and multi-ply floors are getting more and more popular oak flooring has become even less expensive. But engineered birch flooring, would then also become cheap wood flooring if only it arrived on the wooden floor in some good volume. But as it is, it remains a niche and therefore very expensive product. And if thats not strange enough, due to lower volumes this less than high quality engineered wood is considerably less expensive than than its oak engineered flooring rival.
A good insight how a less quality product can become more expensive simple due to volume. Id say buy the oak any day. And if you really like the hard wearing but light floors, just buy some maple.