One reason is that there are effective, inexpensive means for cleaning each of these container types, for example, acid rinsing for polyethylene trace-metal sample bottles. If plastic bottles were used for organic compounds, first, we could not clean them effectively, and second, we would have plasticizer contamination leaching into the water samples, which would interfere with the analysis. Q. Samples are wrapped, packed in ice, and sent overnight mail. Once the sample is removed from the aquifer, lake, or stream, biotic or abiotic degradation can occur, even in the presence of preservatives. Volatile components can outgas, even with tight sealing.
Biotic degradation is promoted by the bottle surface which bacteria can colonize.
If exposed to light, photodegradation is enhanced. And all these processes are favored by increasing temperature. The precautions taken in sample shipping ensure that the sample is received in as close to its original condition at the time of collection as possible. No, the water will not spoil, but there can be losses of analytes, particularly volatile organic compounds. We can not stop loss processes, but by shipping the sample under the conditions described in the previous answer to the question and by analyzing them as quickly as possible, we minimize the impact of losses on the final result.