Many reasons. A typical reason is you (or your limited partners) have a capital gain in the current tax year and are seeking losses to offset this gain and thereby minimize your tax bill.
For example, assume you have a $500,000 taxable gain on a sale of a security. You have a different private investment for which you paid $500,001 that has miniscule likelihood of generating future returns. By selling this holding to CapGain Solutions, you will generate a taxable loss that will offset your capital gain. In states with no related taxes, the loss might be worth approximately $125,000 in Federal tax savings. In states with high tax rates, such as California, your tax savings might be worth over $200,000. This is just an illustrative example only; your circumstances might differ. See other scenarios here. Consult your tax advisor, as CapGain Solutions does not provide accounting or tax advice.