It's the outcome of changing systems.
I was born in the early 70s and taught completely in metric at school. However my parents were taught the imperial system so we were effectively "bilingual" in that we used both systems. It's not about how much easier one is to use it's about what the number/system means to you and if you are able to estimate in that system.
For instance. I understand height in feet and inches. Metres and centimetres don't mean anything to me. I can't really understand exactly how tall that makes someone in reference to everyone else. So for example I immediately know the someone is tall if over 6 foot and short if they are nearing 5 foot. In metres I'd need to convert it to make a judgement. I wouldn't know without a lot of thinking about it.
I do similar with room measurement estimates. I would estimate in feet but if I was measuring a room for carpet. I'd do it in metres as it's easier to work with and lots of shops etc now use metric.
I however do temperature (for weather) in Celsius (or centigrade as I like to call it!). Fahrenheit means nothing to me. I have no idea how hot or cold it will be if you tell me in Fahrenheit. However if we are talking about body temperature I think in Fahrenheit. I know for instance that 100 is something to start worrying about, and 104 is bad, seek help immediately and everything in between. I can't even remember the Celsius equivalent it's a random number like 35.7 or something. Anyhow I have to look it up and even then aren't completely sure if the scale of worry that's needed!
Weight I also do in stones, lbs (and ounces for babies). I understand what that means. What's heavy and what's not. For babies I'd understand 10lbs...That's a big baby and 5lb is on the small side. 3kgs? No idea. Similarly for adult weights. Americans seem to use lbs only for weights...like someone is 145lbs. Again that means nothing to me but I'd understand what 8 stone or 11 stone might look like in terms of weight.
But I tend to cook in metric (again because it's easier to work with)! Although I can use both.
And I think it's going to continue for decades as my DS also understands the above as that's how I talk to him. He seems to understand heights of people in both metres and feet and inches though so it will likely slowly change over time but I think we're a few generations out from imperial being gone for good.