I don't think airport infra was the reason, unless maybe they wanted to preserve the low clearance for operating to airports without proper facilities? One rea

I don't think airport infra was the reason, unless maybe they wanted to preserve the low clearance for operating to airports without proper facilities? One reason was probably that it is technically difficult to fit larger gear as they would not fit in the 737 wheel wells. Or something related to increased height... But in fact it seems the nose gear was actually lengthened somewhat for MAX, but I guess that was not enough. The MAX 10 will also have longer main gear - it will be telescoping so it fits into existing wheel wells. (per https://en.wikipedia.org/wiki/Boeing_737_MAX https://en.wikipedia.org/wiki/Boeing_737_MAX)