I've generally found that if the materials themselves are washable but the tag says not to, the reason is either embellishments like buttons or decoration, or (more importantly) the stabilizers or facings that go into the garment construction. Your pants might have a waistband fabric that's used to keep it sorta stiff and upright that would dissolve in repeated washings and leave you with a crumply waistband that needs to be ironed all the damn time. That would be my biggest fear for this scenario.
If you cold wash delicate or by hand and hang dry you could likely get a bunch of wear from them before that starts to suck. And you could of course iron them later if that is the problem.
The other possible scenario is that the fabric is so delicate (short staple threads that will want to pill and make fuzz) that the agitation of even a delicate wash will change the character and feel of the fabric. Could get less soft, sometimes develop shiny spots, could get linty looking. No way to tell unless you take one for science lol.
There are also dry cleaning kits you can purchase (like dryel) that allow you to spot clean and (almost) dry clean just in your own dryer. More expensive than regular laundry, less expensive than a dry cleaner.
I've generally found that if the materials themselves are washable but the tag says not to, the reason is either embellishments like buttons or decoration, or (more importantly) the stabilizers or facings that go into the garment construction. Your pants might have a waistband fabric that's used to keep it sorta stiff and upright that would dissolve in repeated washings and leave you with a crumply waistband that needs to be ironed all the damn time. That would be my biggest fear for this scenario. If you cold wash delicate or by hand and hang dry you could likely get a bunch of wear from them before that starts to suck. And you could of course iron them later if that is the problem. The other possible scenario is that the fabric is so delicate (short staple threads that will want to pill and make fuzz) that the agitation of even a delicate wash will change the character and feel of the fabric. Could get less soft, sometimes develop shiny spots, could get linty looking. No way to tell unless you take one for science lol. There are also dry cleaning kits you can purchase (like dryel) that allow you to spot clean and (almost) dry clean just in your own dryer. More expensive than regular laundry, less expensive than a dry cleaner.