Why does my Xubuntu LibreOffice look ugly?

My LibreOffice installation looks like Windows 95. The rest of my Xubuntu looks okay. Why? How can I fix it?

^{Click on the image for a full-resolution picture.}

On the screenshot Leafpad and Calculator are open for comparison.

^{Click on the image for a full-resolution picture.}

^{Click on the image for a full-resolution picture.}

By investigating with Synaptic and trial & error method I came up with the solution:

sudo apt-get install libreoffice-style-tango libreoffice-gtk libreoffice-gtk3

I have no idea why these packages were missing. I hope this helps someone.

sudo apt-get install libreoffice-gtk

Also upper command line works for lubuntu (LXDE). For example with flat gtk theme 'victory' and 'papirus' icons LibreOffice looks great.

The minimum requirements to get the correct look for LibreOffice in Xubuntu is libreoffice-gtk along with either libreoffice-style-tango or libreoffice-style-human