From google about selective service:
What Happens If You Don't Register for Selective Service. If you are required to register and you don't, you will not be eligible for federal student aid, federal job training, or a federal job. You may be prosecuted and face a fine of up to $250,000 and/or jail time of up to five years.
Selective service may not be required for H1B but many indians ( up to 75% of indian americans ) have used the H1B to get to permanent residence and citizenship, however after getting permanent residence and citizenship it doesn't look like they are well represented in those who gave life in US wars, that's the point
selective service is for males between 18 and 26
if you get your green card at age 30 you bypass the whole process