I may have found several explanations, but in Bahasa Indonesia (Indonesian language) that may be used by people why they change location between shalah fard and other shalah (nafl or rawwatib), I will translate roughly:
That Day, it (the earth) will report its news
(Qs. Al Zalzalah: 4)
Dari Umar bin Atha' bin Abil Khawar : Bahwa Nafi' bin Jubair pernah mengutusnya
kepada As-Sa'ib Ibnu Ukhti Namr untuk menanyakan sesuatu yang pernah disaksikan
oleh Mua'awiyah darinya dalam shalat. Maka dia menjawab : "Ya, aku memang pernah
mengerjakan shalat Jum'at bersamanya di Al-Masqshurah (rumah benteng besar).
Setelah imam mengucapkan salam, aku berdiri di tempatku dan langsung mengerjakan
shalat. Setelah dia masuk, dia mengutus seseorang kepadaku seraya berkata,
"Janganlah engkau mengulangi perbuatanmu lagi. Jika engkau mengerjakan shalat
Jum'at maka janganlah engkau menyambungnya dengan shalat yang lain sehingga
engkau berbicara atau keluar, karena sesungguhnya Rasulullah Shallallahu 'alaihi
wa sallam memerintahkan kita melakukan hal tersebut, yaitu tidak menyambung
shalat dengan shalat yang lain sehingga kita berbicara atau keluar" Diriwayatkan
oleh Muslim [6]
From 'Umar ibn Atha' bin Abil Khawar: That Nafi 'ibn Jubair had sent him
Ibn As-Sa'ib Ibn ukhti Namr to ask something that has been witnessed
by Mua'awiyah about him in shalah. So he replied: "Yes, I have performed shalah Friday with him at Al-Masqshurah (the fort).
After the imam say salam, I stood up in my place and directly performed
shalah (ba'diyah). After he entered, he sent someone to me and said,
"You should never repeat what you just did. If you pray shalah
Friday, you shall not directly perform another shalah until you
you speak/talk or get out, because the Prophet sallallaahu 'alaihi
wa sallam commanded us to do that, which is we must not perform
a shalah after another one before we speak/talk or get out"
Reported by Muslims [6]
Hadeeth Shaheeh. Narrated by Muslim
in the Kitaabul jumu'a, Ash-Sha chapter; aah ba'dal jumu'a, hadith no. 883
http://www.almanhaj.or.id/content/664/slash/0