Even where the lawyer has exercised his/her utmost due diligence, there are still some risks such as fraud that a lawyer cannot discover from title investigation and many items that are excluded from the lawyer's opinion (such as checking that signatures are genuine and internal corporate approvals and processes have been followed, etc). In many countries in Asia, lawyers are not required to carry professional indemnity insurance, so even in the event that it were possible to prove the lawyer had been negligent, sufficient financial compensation is unlikely to be achieved.
Title insurance provides a "belt and braces" coverage for those items which the solicitor has reviewed, and in addition, additional coverage over other unknown defects. It also provides "No Fault" recovery - there is no need to litigate to prove fault.