Probably the main reason Beyonce can't do opera has a lot to do with that she doesn't need to sing opera to be a successful singer, and she probably doesn't want to. If she hasn't a problem with it, why do you? If you must compare her to other singers, it would be more appropriate to compare her to other R&B and pop artists. She can sing the the hair extensions off Nicki Minaj.
Your first "example" only indicates how thin Beyonce's voice is--not how strong it is. Her low notes are very weak and she can hardly be heard over the guitar.
The second example is pure nonsense--she is again singing with a microphone.
No one is saying Beyonce can't sing, but even at the recent Superbowl, she didn't want to chance singing a live performance of the "Star Spangled Banner". She lip synched her own vocals that were recorded earlier (actually Whitney Houston did the same things years ago).
But you really need to listen to some actual opera singers--attend a couple of live performances of a full production, to get an idea of what opera actually involves and what it's supposed to sound like. You might prefer Beyonce's lighter voice, but it's not suitable for opera. Maybe opera singers shouldn't sing something like "Bootylicious" either, but opera is more than just singing a couple of songs on key and in a high register.
First of all, stop with thinking "high pitches" mean opera. This is an opera singer too:
http://www.youtube.com/watch?v=WvejdHpyofw
Furthermore, in addition to just singing, opera singers need to know several different foreign languages. It's not enough to just learn things phonetically. You have to have adequate understanding of what the heck you're singing (words and phrases can lose meaning in translation).
Here are some examples of other opera singers and how difficult and intricate this music can get. Plus these arias would be part of two to three hour productions.
Joyce DiDonato (mezzo-soprano)--
http://www.youtube.com/watch?v=ysGFMx6NOEY
Beverly Sills (soprano)--I take your Beyonce voice control and raise you one-- especially listen to the held note at 2:36 to 2:59 where she actually gets louder toward the end. By the way, the entire scene is nearly 14 minutes long in which she would be on stage in a heavy costume under lights and singing with no microphones over an orchestra and full chorus.
http://www.youtube.com/watch?v=Xas_7xGcUQU
Natalie Dessay (soprano)--this starts off acapella. Then the orchestra comes in (so the singer had BETTER be on key).
http://www.youtube.com/watch?v=TenJ_F9Tqps
This is soprano Kathleen Battle, whose voice was considered "small" by opera standards--and still isn't using the same sort of microphones as Beyonce needs (any mics are to record the concert).
http://www.youtube.com/watch?v=TF0XSkb7TyM
Probably among the most demanding operatic repertoire, is music written by Richard Wagner. Tackled by only the most powerful and well-trained singers. Skip to 1:24 when Jessye Norman comes in. Notice how open her mouth must be in order to project her voice. Here she is in concert performing another Wagner arias. Wagner operas can be 3 1/2 to 5 hours long (not counting intermissions or how long it would take to do the entire "Ring" cycle). And how long is Beyonce on stage?
http://www.youtube.com/watch?v=swTTWurVnKc
http://www.youtube.com/watch?v=vb_g8GXrZPc
Beyonce is very successful at what she does. All you are doing by constantly insisting she is something she is not, is diminishing what talent she does have by comparing her unfavorably in a medium she never even attempted to venture into.