You are right in that value of equity has not balance
sheet impact. However,low equity value affects the
way a company raise capital. Prime ways for raising
capitals are two:
1. Sell additional/existing shares or;
2. To borrow, to incur debt

High Tech companies with little assets have difficulty
borrowing due to lack of tangible assets as collaterals,
as a result, low share price affect low asset
companies more than asset heavy ones...