Because one do not snore in net but does in real life and it may be an important reason for a fight 
Who knows may be your partner is so keen on his/her sleep? Day by day you may realize that your partner is not the "wonderful one" as you thought upon his/her writings.
You do not write to ask for salt in the table. But your partner may be so harsh when asking for salt in real life?! May be the person who writes unblievably nice things does not ever help you or not self-sacrifising at all. I dont think that tehere is a corelation between pen power and heart power.
Who knows may be your partner is so shy in social life. Or he/she does not actually like to go out in real life as he/she said in net.
Etc. Etc. there are too many variables. All those are unknowns. Although people who spend all days with each other for years can not know each other well, how can it be possible towards writings?
Chat love is sth like two botoxed persons conversation. Nothing is too real or the partners can´t show the reality.
OHHHH bad boy! You only sleep together after marriage, so you will only learn about snoring after you already said "I do". You will not find out that somebody snores on a normal date. Meeting in real life has advantages, meeting online has other advantages. I met my partner in real life, and my hormones swept me away 
But it was actually through internet conversations that I REALLY go to know him. In real life your relationship can be based purely on the physical. On the internet this is impossible.
