Because it's second-guessing Valve's creative decisions, an act made blatantly obvious by baselessly assuming these are "errors" to begin with. Do you think Half-Life was slapped together in a week by a bunch of clueless yokels? That seems to be the impression many people have now when they compare it to Valve of today, comprised of hundreds of employees and the King of Steam and all that. However, such a sentiment couldn't be farther from the truth. Back then, there were a number of remarkably talented individuals behind the scenes who were capable of developing a damn good game. And those people knew what they were doing.
The HEV suit was one of many ideas that went through several design iterations (read Raising the Bar, see Ivan), yet this is how we ended up receiving it. So yes, the HEV suit is supposed to look like it does. There were no accidents or mistakes made. It's meant to look like that because that's how Valve wanted it to look. The BMS team isn't Valve, yet they're making changes by the boatload as if the original developers can't be trusted, as if the source material means nothing to them, as if they know better than Valve did. I'm not claiming Half-Life is perfect and that it couldn't be improved, but at the rate Black Mesa is going, there's going to be a point one day when you'll take a step back looking at it all and wonder, "Is this still supposed to be Half-Life?"
You are acting like the Black Mesa team is working for Valve and it has to be like what Valve made it