... as an independent contractor ... working from home
I am not US Citizen and my country has no tax treaty with USA.
I currently live outside USA and I do not plan to travel in near future.
Does IRS require the 30% ...
No. If you as a nonresident alien are paid (by a US entity) for services performed outside the US, the income is not US 'source' and there is no US tax. See chapter 2 of pub 519. (At least assuming your plan is carried out. What matters is what you do not what you plan or planned.)
... on the official IRS website it says that all foreign non resident aliens are subject to 30% withholding tax. Maybe this does work if the person is inside USA or doing business in USA,
Cite? I've never seen any statement that all nonresident aliens pay 30% on everything; the rules are much more complicated. Pub 519, linked above, is mostly about nonresident aliens and in printed or PDF form (also available from the IRS website, including prior years) is 68 pages. Re your second statement, if you are resident in the US for tax purposes, which is itself determined by fairly complicated rules and is not as simple as just being 'inside' US (and BTW also not the same as permanent residence for immigration purposes, don't get them mixed up) -- or operate a trade or business in the US (as opposed to merely doing business with a US entity, as in your case) -- then you are taxed as a resident, at progressive rates that vary depending on the amount and type(s) of income after deductions and less credits but are nearly always less than 30%.
Also there is an important difference between withholding and tax here. Withholding is only an estimate, and can be wrong, especially for residents and citizens. As an NRA, if you are entitled to a treaty rate on say dividends or rents but don't claim it on W-8BEN, then the payer must withhold at 30%, but you can file a tax return (1040NR) after the end of the year (and within 3 years) to compute the correct, lower tax and get a refund of any withholding beyond the correct amount. (One caveat: domestic taxpayers get credit for amounts withheld even if the withholder didn't actually pay the withheld money to IRS/Treasury as required, for example because the business went bankrupt or the owner absconded to North Korea. IRS takes the position that NRAs only get withholding credit for money actually paid in, although the Taxpayer Advocate has begun complaining about this and might be able to get it changed. Also note that if you don't have and use a US bank account your refund will take the form of a paper US Treasury check, and this site has several Qs already about people in other countries having difficulty cashing a US Treasury check.) This is different for taxes other than income tax. For Social Security and Medicare taxes (together called FICA) the amount withheld is the correct tax with one exception: if you work for multiple employers during a year with total income over the yearly wage cap, currently about $130k, the SS withholding will be excessive and you get the excess back on your income tax return (now only 1040 because the shorter forms 1040A and 1040EZ have been eliminated). For the highway fuel tax (often called 'gasoline' tax although that's not exactly correct) the tax is taken out of your purchase price at the pump and is correct -- unless the fuel is actually used off-road, like agriculture or boating, and then you can get it back. Similarly for sales tax (imposed by states and some cities or localities but not Federally) the correct tax is taken out of your payment.