Not all science is done in a lab. Replicating an experiment is obviously feasible for a short term psychology experiment, but in earth sciences (oceanography for instance.) it is far less often possible to reproduce an experiment for the following reasons.
N.B. This is all from my personal experience of one field of science.
1.) Cost. If you got funding to take an ice-breaker to Antarctica to "do science" it required several million dollars to fund. It is difficult enough to secure funding for anything these days, none the less prohibitively expensive attempts to reproduce results. (honestly any serious research vessel will run costs into the millions, regardless of destination.)
2.) Time. Say you are on a research vessel taking measurements of the Amazon river basin. This is a trip that takes months to years to plan and execute. If you return to duplicate your experiment 2 years later, the ecology of the area you were taking measurements of may have changed completely.
3.) Politics. Earth sciences often require cooperation from foreign entities, many of which are not particularly stable, or whom may be engaging in political machinations that run counter to your nationality's presence in the country, or both. Iran and China are two good examples. Both are home to some excellent oceanographers, and both of which can be very difficult to Science in when your team includes non Iranian/Chinese nationalities.