Even if they don't care, there is a responsibility by the researchers to the participants to protect their identity. Your participation in a study may have no big effect right now, but down the line it could. If your project has federal funding and involves research on people, there are ethical requirements and trainings required before starting the study.
What if you completed a simple survey for a study and identified yourself as a member of a group (Christian, Jewish, Mexican, African American, etc.) and 5 years down the line, there was a big rounding up of your group. Suddenly your participation 5 years ago is leading to terrible life changes.
Please get to know participant protections more. They are very important for the integrity of the data used in academia. The NIH has a strict policies to ensure the safety of participants.
The Institutional Review Board (IRB) reviews studies for risks participants could face as a result of participating. Every person who has access to the de-anonymized data must complete an NIH training course.
Depending on your institution, the process varies in seriousness. Having worked on 2 submissions and helped on ~3 other IRB approved studies, it can be tedious. My institution takes 6+ weeks from submission to approval, which can really delay things. At the same time, it's a vital part of the process to ensure validity.