Biologists modify cells so that we can study them. The modifications are about 0.00001% effective. If you attempt to modify 10^6 cells then maybe 20 cells will be modified. Most cells do not take the modification. So you need to select out the individual cells that have been modified.

You do this by including antibiotic resistance genes alongside your modification. Now all modified cells are resistant to the antibiotic. Then you apply a small amount antibiotic to kill the unmodified cells. Now you only have the cells with your interesting modification.

This is the mainstay of molecular biology. Every lab biologist has done it. We even do it as college students in lab practicals.

Banning the use of antibiotic resistance genes in biological research is effectively banning all wet lab medical research.