Why are mosques beautiful?

Answer 1

No. But if you want to have any tourist action then, yes. Mosques do not need to beautiful. Of course they would look more attractive if they were and this might attract believers. But, it is not how the mosque looks but how many people attend the congregation and what is inside. Where I live there is a lovely mosque but you cannot tell that it is a mosque, it looks more like a social house or church.

Answer 2

Because mosque is a place for praying and that God is beautiful and likes beauty, and He is kind and doesn't accept but kind things.

18. He only shall tend Allah's sanctuaries who believeth in Allah and the Last Day and observeth proper worship and payeth the poor-due and feareth none save Allah. For such (only) is it possible that they can be of the rightly guided.

31. O Children of Adam! Look to your adornment at every place of worship, and eat and drink, but be not prodigal. Lo! He loveth not the prodigals.

[quoted from, Meanings of the Glorious Quran, by Marmaduke Pickthall]
why are churches beautiful?

mosques are just buildings man, but just like there is a spanish way, an Egyptian way there is an Arab way that was highly influenced by other cultures Islam have invaded and concurred.