When I first got to Germany and was 16 and was drinking beer because the legal alcohol drinking age is 16, people did this cheers thing before drinking. I thought it was just like what Ive seen before in America and just clanked the glass and said Prost back at my friends. Immediately after, they all commented on the fact that I did not look at them in the eyes and told me that I should always look people in the eyes when Prosting. Though they did not explain why, I imagine it was just a cultural tradition/etiquette thing. After that incident, I took my friends advice and did that every single time afterwards. I realized everyone did really look at you in the eyes when Prosting and assumed that was probably a really important thing to do in Germany.
The informant thinks its rather different from what we do here in the states in that it shows a more direct connection with ones friends while drinking. It probably also emphasizes the way German people interact. Since looking away or indirectly at ones eyes may indicate deceit or suspicion, it would only make sense that when toasting with friends, the least one can do is to make some eye contact.
Paradigmatically, looking at German culture as a whole, I think it makes a lot of sense that there is a lot of importance placed on drinking etiquette. Personally, I also find the eye contact fascinating because some cultures might actually take offense to that. While in Germany, toasting and looking directly at someone might signify friendship and honesty, perhaps in other cultures it might be considered rude to stare.