The push for biologics is simply because they work best. Kids tend to have worse prognosis than adults - pediatric IBD can be aggressive and it can spread to different parts of the bowel (for example, a young child may initially have colonic disease and over time it may spread to small bowel, whereas in adults, it tends to stay in the same place as where it is diagnosed). They also face complications adults do not - with growth and development. So pediatric GIs aim to get the disease under control quickly, so the child can grow and develop normally. The window of growth is short, so if your child is a teen, your GI probably wants to get the disease under control so he or her can grow to their full potential. In addition to growth, there’s also bone density that they track and of course regular development.
My daughter was very underweight for a while and her bone density became very low - she was so malnourished. Luckily, she was young enough that she was able to gain bone density as she gained weight (which she did using supplemental formula and an otherwise relatively normal diet). But had she been older, by even a few years, she may not have been able to regain that bone density and would have had osteopenia for life.
The best diet for IBD is EEN - only formula, NO food. That is used to induce remission and it certainly works very well - it’s usually used for 6-8 weeks. But it is hard on kids and continuing it indefinitely is not possible for most kids. My daughter found it extremely hard as a teenager and as a young adult. Supplemental formula was easier - that was in addition to food and that helped her gain weight.
All of us are afraid of the meds when our children are diagnosed, but what we quickly realized is that the disease is far scarier than the medications. Damage to the intestines is permanent and complications like strictures, fistulae and abscesses often require surgery and hospitalizations. The goal is to get control of the disease before it causes those complications and honestly, biologics are the best meds to do that. The alternative is immunomodulators, 6MP, which isn’t used in teen boys in particular because it can cause a very rare type of cancer and Methotrexate, which is a good med, but comes with more side effects and works much more slowly than biologics. Both my daughters have been on biologics for over 10 years and both would say that going on biologics was completely life-changing and the best decision we ever made.