What is the perspective of the western buddhist cannon websites? In the eastern perspective, Tipitaka is memorized and studied by Atthakatha-teachers from generation to generation and still going on nowadays, so it is weird to study Tipitaka without Atthakatha. 

But I look at the western Buddhist canon website and they look like "these words are from his disciple's mouth, but I don't want to hear his disciple's explanation because it's not actually his."

For the example, https://suttacentral.net/ protects 84000.org to show suttacentral's page on its iframe directly after this function opened ere long. 

I requested this function to 84000.org webmaster because I need to use tipitaka, atthakatha, and tika in pali thai, pali roman, siamrattha thai translation, mahamakutta thai university translation, MCU translation, and english translation. (I don't know why 84000.org chose iframe instead of the real source from inside, but I think the webmaster may avoid the license problem).

Actually, that protection is not the main idea, however it means suttacentral webmasters already knew the problem that suttacentral has not enough canons for the reference, no Atthakatha-pali and no Tika. It's ok for that protection, but it makes the questions that why don't suttacentral and the other western buddhist canon websites put the losing resources into their website, although they already knew there were demands?

So, 


What is the perspective of the western Buddhist canon website to protect the Buddhist people from Atthakatha study?
Why the western Buddhist canon website acts like  "these words are from his disciple's mouth, but I don't want to hear his disciple's explanation because it's not actually his"?


Another, why don't the western Buddhist canon websites make the function for easier reference such as highlight function?
OP: It's ok for that protection, but it makes the questions that why don't suttacentral and the other western buddhist canon websites
  put the losing resources into their website, although they already
  knew there were demands?
  
  OP: Another, why don't the western Buddhist canon websites make the function for easier reference such as highlight function?


SuttaCentral for example, has a discussion forum here. If you want new features. You can ask them directly. I'm sure other "western" buddhist canon websites have similarly reachable community or administrators. If they lack manpower, maybe they will focus on the canon first, which is itself huge.

Apart from the suttas, there's also translation of the Visuddhimagga online and also summaries of the Abhidhamma.


  OP: What is the perspective of the western Buddhist canon website to protect the Buddhist people from Atthakatha study?


I think this is largely due a lack of manpower, so they focus on what they think people need the most.

For example, you can see that not all of the Sutta Pitaka is available on AccessToInsight. Only the ones judged by the admin to be the most useful are there. Similarly with Piya Tan's collection at The Minding Centre.

On the other hand, SuttaCentral has grown to contain a far bigger collection of the suttas, perhaps hoping to cover the whole Sutta Pitaka one day. This is by itself a huge effort.

Comparatively, the Atthakatha is seen as secondary to the Suttas and less important. 

But nevertheless you can read parts of the Atthakatha indirectly quoted by Piya Tan at The Minding Centre and other translators like Thanissaro Bhikkhu on AccessToInsight.


  OP: Why the western Buddhist canon website acts like "these words are from his disciple's mouth, but I don't want to hear his disciple's
  explanation because it's not actually his"?


I don't think this is the attitude. I think it's more like "I want to listen to the master's words first. That's more important to me. But if there is a disciple explaining it, I can refer to it, but it's less important or secondary."