system
Given the following post, respond as if you're commenting on Reddit:
human
[40k] Why did the Emperor build a new portal into the Webway instead of just capturing an Eldar portal?
gpt
Eldar portals are very, very high tech. Most likely directly based on the ones build by their creators.

It would be foolish to simply steal enemy technology and use it as your own without understanding the working principles behind it and adapting it to your needs. There could be traps build in or the use simply deadly to any different species after all.

So you capture a gate, dissect and study it and then build your own based on the findings. Which is what he did.