Any reason to have multiple goo or science jr containers on non-returning ships?

[Oddible]

So I've been loading up my ships with multiple science containers and it occurred to me that this doesn't really have any positive effect (except maybe balance). I open two Science Jrs and transmit, it is the same as when I just open one twice. Same for goo. I'm adjusting all my non-returning probes now and scaling back their science multiples.

[Kasuha]

Opening one twice has the same scientific output like opening two once - but you save on transmit time because they are sent in the same transmission. And if you are in tight situation, e.g. sun below horizon and you're short on batteries, you can have two doses of science stored in them instead of one. This came handy when I was descending to Eve and had to stow my solar panels, I did as much low atmosphere science as my batteries allowed to transmit and kept the rest for the surface when I can open panels and recharge batteries for further transmission.

The main reason to have science equips twice, though, is to have things balanced.

[Oddible]

Opening one twice has the same scientific output like opening two once - but you save on transmit time because they are sent in the same transmission.

Great answer, and I really wanted it to be the case, but I don't think it is correct. I just tested my probe orbiting Duna which has 4 goo pods. I examined each of the 4 goo pods and selected Keep Data. Then I went to my antenna and selected Transmit Data. Instead of transmitting all at once, it just did what it normally does when you transmit for each goo pod. It transmitted 4 times in succession.

Would be a really great thing to implement!

[KerbMav]

Doing all inter-atmospheric experiments faster as Kasuha wrote, balancing the craft, redundance for half-landings ... but from a pure game-mechanics point of view - no, no need to do so.

[Kasuha]

It transmitted 4 times in succession.

Yes but it did not stow the antenna in between them. That's what I meant by single transmission.