Hive Engine did an excellent job of providing sub-tokens to the community while STINC failed to deliver for years. This is why I find the criticism from some people in this community a bit disrespectful. @aggroed gave projects life, and in return he gets shit. Not really a nice gesture. Anyway, regarding your questions:

Why am I not using HE or why am I not a HE Witness?

I'm not using it, as I don't want to create a (token-) project just for the sake of creating a (token-)project. (This goes for any token standards btw - ERC20 & co.) And since I'm not using it, there's no reason for me to provide governance and earn money in/from a community I'm not active in.

Why don't I hold any HE tokens?

I'm conservative in my token holdings. HE tokens could be on ETH or BSC, wouldn't change much for me.

Cubdefi is buying an Audit, why not HE?

CubDefi forked from GooseDefi, which forked from PancakeSwap, which I think forked from Sushiswap (?), which forked from Uniswap.

I'm not sure whether CubDefi changed something within their Contract. But even if they did, all of the previous forks have audits themselves, so there's kind of an already existing infrastructure for Solidity Smart Contracts.

Hive Engine on the other hand was built from the ground up by people @aggroed hired, which means it uses a completely different code-base, Smart Contract language (JS instead of Solidity) etc. Keep in mind that HE started quite a few years ago, so at that point, there was probably no other option than actually building something from scratch.

With this said, I'm not in the loop about Hive Engine, so I'll refrain from commenting further.